[Federal Register Volume 68, Number 7 (Friday, January 10, 2003)]
[Proposed Rules]
[Pages 1399-1414]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-372]


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DEPARTMENT OF LABOR

Occupational Safety and Health Administration

29 CFR Part 1910

[Docket No. S-550]
RIN 1218-AB97


Commercial Diving Operations

AGENCY: Occupational Safety and Health Administration (OSHA), 
Department of Labor.

ACTION: Proposed rule; request for comments and scheduling of informal 
public hearings.

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SUMMARY: OSHA is proposing to amend its Commercial Diving Operations 
standards to allow employers of recreational diving instructors and 
diving guides to use an alternative to the decompression-chamber 
requirements for post-dive procedures and mixed-gas diving. The 
proposed alternative would apply only when these employees are engaging 
in recreational diving instruction and diving guide duties using an 
open-circuit, a semi-closed-circuit, or a closed-circuit self-contained 
underwater breathing apparatus supplied with a breathing gas consisting 
of a high percentage of oxygen mixed with nitrogen.

DATES: Submit written hearing requests and comments regarding this 
proposal, including comments on the information-collection 
determination described in Section V of the preamble (``Paperwork 
Reduction Act),'' by the following dates:
    Hard copy. Submitted (postmarked or sent) by April 10, 2003.
    Facsimile and electronic transmission. Sent by April 10, 2003.
    Please see the section entitled ``Supplementary Information'' below 
for additional information on submitting written comments and hearing 
requests.

ADDRESSES: Comments and Attachments: Regular mail, express delivery, 
hand-delivery, and messenger service. Submit three copies of written 
comments and attachments to the OSHA Docket Office, Docket No. S-550, 
Technical Data Center, Room N-2625, U.S. Department of Labor, 200 
Constitution Ave., NW., Washington, DC 20210; telephone (202) 693-2350. 
OSHA Docket Office and Department of Labor hours of operation are 8:15 
a.m. to 4:45 p.m., EST.
    Please note that security-related problems may result in 
significant delays in receiving comments and other written materials by 
regular mail. Telephone the OSHA Docket Office at (202) 693-2350 for 
information regarding security procedures concerning delivery of 
materials by express delivery, hand delivery, and messenger service.
    Facsimile. Transmit written comments (including attachments) 
consisting of 10 or fewer pages by facsimile to the OSHA Docket Office 
at (202) 693-1648. You must include the docket number of this notice, 
Docket No. S-550, in your comments.
    Electronic. Submit comments electronically through the Internet at 
http://ecomments.osha.gov. Please note that you cannot attach materials 
such as studies or journal articles to electronic comments. If you have 
such materials, you must submit three copies of them to the OSHA Docket 
Office at the address above. These materials must clearly identify your 
electronic comments by name, date, subject, and docket number so we can 
attach them to your comments.
    All comments and submissions will be available for inspection and 
copying in the OSHA Docket Office at the address above. Comments and 
submissions posted on OSHA's Web page will be available at http://www.osha.gov. Contact the OSHA Docket Office at (202) 693-2350 for 
information about materials not available on the OSHA Web page and for 
assistance in using this Web page to locate docket submissions. Because 
comments sent to the docket or to OSHA's Web page are available for 
public inspection, the Agency cautions interested parties against 
including in these comments personal information such as social 
security numbers and birth dates.
    Hearing Requests: Send hearing requests in quadruplicate to 
Ms.Veneta E. Chatmon, Office of Public Affairs, Docket No. S-550, Room 
N-3649, OSHA, U.S. Department of Labor, 200 Constitution Avenue, NW., 
Washington, DC 20210; telephone (202) 693-1999. Interested parties may 
transmit these requests by facsimile to Ms. Chatmon at (202) 693-1634.

FOR FURTHER INFORMATION: For general information and press inquiries, 
contact Ms. Bonnie Friedman, Office of Information and Consumer 
Affairs, Room N-3647, OSHA, U.S. Department of Labor, 200 Constitution 
Avenue, NW., Washington, DC 20210; telephone (202) 693-1999. For 
technical inquiries, contact Ms. Joanne Slattery, Directorate of 
Standards and Guidance, Room N-3609, OSHA, U.S. Department of Labor, 
200 Constitution Avenue, NW., Washington, DC 20210; telephone (202) 
693-2056 or fax (202) 693-1663. Copies of this Federal Register notice 
are available from the OSHA Office of Publications, Room N-3101, U.S. 
Department of Labor, 200 Constitution Avenue, NW., Washington DC 20210; 
telephone (202) 693-1888. For an electronic copy of this notice, go to 
OSHA's Web site (http://www.osha.gov), and select ``Federal Register,'' 
``Date of Publication,'' and then ``2002.''

SUPPLEMENTARY INFORMATION:

Table of Contents

    The following Table of Contents identifies the major sections under 
SUPPLEMENTARY INFORMATION including the summary and explanation and the 
regulatory text of the proposed application provisions and alternative.

[[Page 1400]]

I. Background
II. Summary and Explanation of the Proposal
    A. Proposed Sec. Sec.  1910.401(a)(3) and 1910.402 
(``Definitions'')
    B. Alternative Conditions of Proposed Appendix C
    1. Equipment Requirements for Rebreathers
    2. Special Requirements for Closed-Circuit Rebreathers
    3. O2 Concentration in the Breathing Gas
    4. Limiting O2 Partial Pressure and Diving Depth
    5. Mixing and Analyzing the Breathing Gas
    6. Use of No-Decompression Limits
    7. Emergency Egress
    8. Treating Diving-Related Medical Emergencies
    9. Diving Logs and Decompression Tables
    10. Diver Training
    11. Testing Protocol for Determining the CO2 Limits 
of Rebreather Canisters
III. References
IV. Legal Considerations
V. Preliminary Economic Analysis and Regulatory Flexibility 
Certification
VI. Paperwork Reduction Act
VII. Federalism
VIII. State Plans
IX. Unfunded Mandates
X. Applicability of Existing Consensus Standards
XI. Public Participation
    List of Subjects in 29 CFR Part 1910
    Authority and Signature
XII. Proposed Amendment to the Standard

I. Background

    The Agency published a final rule in 1977 regulating the 
occupational safety and health employees engaged in commercial diving 
operations under 29 CFR part 1910, subpart T (42 FR 37668). In 1999, 
acting under Section 6(d) of the Occupational Safety and Health Act of 
1970 (``OSH Act''; 29 U.S.C. 655), OSHA published an order granting a 
permanent variance to Dixie Divers, Inc. (``Dixie'') (Ex. 2-11). The 
permanent variance exempted Dixie from OSHA's decompression-chamber 
requirements specified at Sec.  1910.423(b)(2) and (c)(3)(iii), and 
Sec.  1910.426(b)(1) when its recreational diving instructors and 
diving guides engage in underwater instructional and guiding 
operations. The variance applies only to mixed-gas diving operations at 
a maximum depth of 130 feet of sea water (``fsw'') performed within the 
no-decompression limits; employees used a breathing-gas mixture 
consisting of a high percentage of O2 mixed with nitrogen 
(i.e., a nitrox breathing-gas mixture) supplied by an open-circuit, 
semi-closed-circuit or closed-circuit SCUBA. In issuing the permanent 
variance, the Agency noted that it met or exceeded the level of 
protection afforded by OSHA's decompression-chamber requirements.
    In a letter dated February 4, 2000, Mr. Jeff Nadler, Vice President 
of the Professional Association of Diving Instructors Americas, 
requested guidance from OSHA regarding other employers of recreational 
diving instructors who complied with the conditions of the permanent 
variance granted to Dixie (Ex. 3-1). The Agency responded to Mr. Nadler 
on May 3, 2000, stating that it would consider such employers ``to be 
in de minimis violation of the decompression-chamber requirements 
specified at paragraphs (b)(2) and (c)(3)(iii) of Sec.  1910.423(b)(2), 
and paragraph (b)(1) of Sec.  1910.426(b)(1).'' OSHA noted that ``[d]e 
minimis violations carry no penalties, do not require abatement and no 
citations are issued.''
    While the de minimis policy may provide regulatory relief to some 
employers, it has several disadvantages. For example, many employers 
prefer not to invoke the policy because they remain in violation of the 
applicable standard even though the violation is only ``technical'' and 
has no enforcement consequences (see OSHA's ``Field Inspection 
Reference Manual,'' chapter III, paragraph C.2.g. (September 26, 
1994)). Additionally, some employers may not know of the policy and, 
therefore, are unable to benefit from it. Accordingly, the Agency is 
now proposing to amend its Commercial Diving Operations (``CDO'') 
standards to incorporate the terms and conditions of the Dixie Divers 
variance into the standard itself. OSHA believes that the proposed 
amendment would improve the effectiveness of recreational diving 
instructors and diving guides by enabling them to remain at the maximum 
diving depth without developing decompression sickness (``DCS'') or 
arterial gas embolism (``AGE'') when they return to the surface. By 
preventing DCS and AGE under these conditions, the proposed amendment 
would make a decompression chamber near the dive site unnecessary for 
these divers.

II. Summary and Explanation of the Proposal

    OSHA has now had nearly three years of experience with the 
conditions of the permanent variance granted to Dixie (and with the 
subsequent application of these conditions by other employers under the 
de minimis policy). Based on this experience, the Agency believes that 
diving operations involving recreational instruction and guiding, when 
performed under the alternative conditions specified in this proposed 
rule, either meet or exceed the level of employee protection afforded 
by the diving standard's decompression-chamber requirements. The 
purpose of having a decompression chamber available and ready for use 
at the dive site is to treat DCS, which may occur from breathing air or 
mixed gases at diving depths and durations that require decompression, 
and AGE, which may result from over-pressurizing the lungs, usually 
while ascending rapidly to the surface during a dive.
    As with the permanent variance granted to Dixie, this proposed 
rulemaking would impose a number of conditions on employers of 
recreational diving instructors and diving guides. The following 
sections describe these conditions, and provide the rationale for 
including them in this proposal.

A. Proposed Sec. Sec.  1910.401(a)(3) and 1910.402 (``Definitions'')

    Proposed Sec.  1910.401(a)(3) specifies that this regulatory 
alternative would apply only to recreational diving instructors and 
diving guides who are engaging solely in recreational diving 
instruction and dive-guiding operations. In this regard, OSHA is 
proposing to add definitions of ``recreational diving instruction'' and 
``dive-guiding operations'' to Sec.  1910.402 of the CDO standards to 
clarify the application of the proposed alternative. Accordingly, 
``recreational diving instruction'' would mean the training of diving 
students in the use of recreational diving procedures and the safe 
operation of diving equipment, including open-circuit, semi-closed-
circuit, or closed-circuit SCUBA during dives; additionally, ``dive-
guiding operations'' would mean the leading of groups of trained sports 
divers, who use open-circuit, semi-closed-circuit, or closed-circuit 
SCUBA, to local undersea diving locations for recreational purposes. In 
addition, proposed Sec.  1910.401(a)(3) requires that employers ensure 
that the instructors and guides conduct these dives within the no-
decompression limits, and use a nitrox breathing-gas mixture consisting 
of a high percentage of O2 (more than 22% by volume) mixed 
with nitrogen and supplied by an open-circuit, semi-closed-circuit, or 
closed-circuit self-contained underwater breathing apparatus; employers 
also must comply with the requirements specified in Appendix C of 
subpart T.
    As noted in the Dixie Diver variance (64 FR 71257), OSHA believes 
that by limiting application of the proposed alternative as discussed 
above, recreational diving instructors and diving guides who dive 
according to the proposed requirements would receive a level of safety 
and protection equivalent to recreational diving instructors who are 
exempted from the CDO standards altogether under Sec.  
1910.401(a)(2)(i); the recreational diving instructors covered

[[Page 1401]]

by Sec.  1910.401(a)(2)(i) must use compressed air supplied to open-
circuit SCUBAs under no-decompression diving limits. Therefore, under 
the proposed alternative, the Agency would not require employers to 
maintain a decompression chamber at the dive site when they comply with 
the specified requirements because it believes that compliance with 
these requirements will reduce the risk of AGE and DCS to the minimal 
levels already experienced by recreational diving instructors covered 
by Sec.  1910.401(a)(2)(i).

B. Alternative Conditions of Proposed Appendix C

    Proposed Appendix C would be mandatory for any employer who uses 
the alternative means of compliance for recreational diving instructors 
and diving guides. The following section sets out the requirements in 
proposed Appendix C, and provides the rationale for each requirement.
1. Equipment Requirements for Rebreathers
    (a) Manufacturer's instructions. Proposed Condition 1(a) requires 
employers to ensure that their recreational diving instructors and 
diving guides (hereafter, ``divers'') use rebreathers (i.e., semi-
closed circuit and closed-circuit SCUBA) according to the rebreather 
manufacturer's instructions. The manufacturers of these rebreathers 
select and develop the characteristics and parameters of SCUBA 
equipment, design and integrate the equipment accordingly, procure or 
manufacture the equipment components, and then assemble and test the 
final products. Accordingly, a wide range of SCUBA designs and 
capabilities are available, and no uniform standards govern the design, 
function, and use of this equipment. Therefore, OSHA believes that the 
SCUBA manufacturer is in the best position to identify and specify the 
components, configuration, and operation of its product, a position 
that several SCUBA manufacturers endorse (see Ex. 3-4, p. 14-2).
    (b) Counterlungs. Under the proposed condition, employers must 
ensure that each rebreather has a counterlung (also referred to as an 
``inhalation bag'' or ``breathing bag'') that supplies a sufficient 
volume of breathing gas to the divers to sustain their respiration 
rate, and that contains a baffle system that prevents moisture from 
entering the scrubber or breathing hoses. Counterlungs are low-
breathing-resistance reservoirs that supply the nitrox breathing-gas 
mixture to a diver during inhalation; accordingly, the National Oceanic 
and Atmospheric Administration (NOAA) considers counterlungs a 
necessity for rebreather diving (see Ex. 3-12, p. 14-3).
    While the proposed condition does not specify a particular 
counterlung configuration, it would require that the counterlung have a 
minimum volumetric displacement sufficient to sustain a diver's 
respiration rate during diving operations. In this regard, OSHA 
believes that rebreather manufacturers currently provide this 
information as a usual and customary practice. Accordingly, the 
proposal would require the employer to ensure that its divers' 
rebreathers have adequate counterlung volume, and that their divers use 
the rebreathers according to the manufacturer's instructions. The 
employer of these divers is in the best position to determine the 
respiratory requirements associated with their diving operations, and 
to identify and select a rebreather based on these requirements.
    The proposed condition also specifies that a rebreather must 
contain a baffle system that keeps moisture from entering the scrubber. 
Accordingly, the proposed baffle system would prevent rapid 
deterioration of the CO2-sorbent material housed in the 
scrubber, thereby decreasing the risk of CO2 toxicity (see 
Ex. 3-12, p. 14-8).
    (c) Moisture traps. Proposed Condition 1(c) requires that the 
employer use a moisture trap in the breathing loop of each rebreather, 
and that both the moisture trap and its location in the breathing loop 
be approved by the rebreather manufacturer. Moisture traps are 
necessary to keep water out of the CO2-absorbing canisters; 
when such water leakage occurs, it can substantially reduce the 
CO2-absorbing properties of the sorbent material inside the 
canister. Evidence from the record of the Dixie Diver variance 
proceedings (Exs. 3-5, 3-6, and 3-7) indicates that moisture traps are 
available commercially and that existing rebreathers routinely use 
them.
    (d) Moisture sensors. Under proposed Condition 1(d), employers must 
ensure that each rebreather has a continuously functioning moisture 
sensor that connects to a visual (e.g., digital, graphic, or analog) or 
auditory (e.g., voice, pure tone) alarm that warns divers of moisture 
in the breathing loop in sufficient time to terminate the dive and 
return safely to the surface. Moisture sensors detect excessive water 
leakage into the canister that can compromise the CO2-
sorbent material; therefore, they supplement the information provided 
by CO2 sensors (see proposed Condition 1(e) below). 
Therefore, moisture sensors warn divers of hazardous water leakage into 
the canister, allowing them to return to the surface before 
CO2 in the recycled breathing gas reaches dangerous levels. 
Information submitted in response to the Dixie's variance request (Ex. 
3-7) indicates that moisture sensors are commercially available.
    Rebreather manufacturers determine the appropriate design and 
location of moisture sensors and moisture traps for their products. The 
proposal requires employers to ensure that their divers use these 
components consistent with the rebreather manufacturer's instructions. 
The moisture sensor must alert the diver of moisture in the breathing 
loop in sufficient time to terminate the dive and return safely to the 
surface.
    (e) CO2 sensors. An important component in controlling 
excessive CO2 is the CO2 sensor. Proposed 
Condition 1(e) specifies that employers must ensure that each 
rebreather contains a continuously functioning CO2 sensor in 
the breathing loop, and that the rebreather manufacturer has approved 
the CO2 sensor and its location in the breathing loop. 
Additionally, employers must integrate this CO2 sensor with 
an alarm that operates in a visual (e.g., digital, graphic, or analog) 
or auditory (e.g., voice, pure tone) mode, is readily detectable by 
divers under the diving conditions in which they operate, and remains 
continuously activated when the inhaled CO2 level reaches 
and exceeds 0.005 atmospheres absolute (``ATA'').\1\
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    \1\ ATA, as used in this notice, is the partial pressure of a 
constituent gas in the total pressure of a breathing gas. When the 
percentage of the constituent gas in the breathing gas remains 
constant throughout a dive, its partial pressure or ATA, increases 
in direct proportion to increases in diving depth.
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    (f) Calibrating CO2 sensors. To ensure that 
CO2 sensors operate correctly, proposed Condition 1(f) 
states that employers must, before each day's diving operations (and 
more often when necessary) calibrate each CO2 sensor 
according to the sensor manufacturer's instructions. In doing so, they 
are to maintain the accuracy of the equipment and procedures used to 
perform the calibration to within 10% of a CO2 concentration 
of 0.005 atmospheres absolute or less according to the sensor 
manufacturer's instructions. Using this equipment, they must calibrate 
the CO2 sensor to within 10% of a CO2 
concentration of 0.005 ATA or less.
    (g) Faulty CO2 sensors. When a sensor fails to meet this 
accuracy standard, proposed Condition 1(g) requires employers to 
replace the faulty sensor, and to ensure the accuracy of the

[[Page 1402]]

replacement sensor before placing the rebreather in operation. 
Determining the accuracy of CO2 sensors is necessary to 
enable employers to eliminate sensors that are unreliable or that 
cannot function under rugged diving conditions. Using a test or 
standard gas containing a CO2 concentration of 0.005 ATA or 
less will ensure that the sensors can accurately detect CO2 
levels that can be harmful to the divers (see Ex. 3-12, p. 3-10). In 
view of the harmful effects that can result from high levels of 
CO2, the sensors need to have a maximum error rate of no 
more than 10% of a CO2 partial pressure of 0.005 ATA. This 
limit would provide an adequate safety margin to allow employees to 
detect CO2 accumulation, make a preliminary effort to 
identify the cause and adjust breathing-system controls, and ascend to 
the surface if necessary.
    (h) CO2-sorbent materials. This proposed condition 
allows employers to implement the manufacturers' schedules for 
replacing the canister of CO2-sorbent material in the 
rebreather as an alternative to using continuously functioning 
CO2 sensors (see proposed Condition 1(e)). The proposed 
condition permits employers to use such a schedule only after the 
rebreather manufacturer develops the schedule according to the 
canister-testing protocol specified below in proposed Condition 11. 
This proposed requirement would ensure that the canister-replacement 
schedule meets quality-control criteria, including an assessment of the 
physical properties of the CO2-sorbent material and an 
evaluation of the canister's effectiveness using a standard canister-
testing protocol (e.g., see proposed Condition 11 (``Testing Protocol 
for Determining the CO2 Limits of Rebreather Canisters''). 
The protocol would permit the employer to make reliable estimates of 
canister duration, thereby allowing replacement of the canister before 
the CO2-sorbent material fails and the diver breathes 
excessive levels of CO2.
    (i) Commercially pre-packed cartridges. When the employer uses a 
CO2-sorbent replacement schedule, proposed Condition 1(i) 
requires the employer to ensure that each rebreather uses a 
manufactured (i.e., commercially pre-packed), disposable scrubber 
cartridge. This cartridge must contain a CO2-sorbent 
material that is approved by the rebreather manufacturer and is capable 
of removing CO2 from the divers' exhaled gas. In this 
regard, the canister must maintain the CO2 level in the 
breathable gas (i.e., the gas a diver is inhaling directly from the 
regulator) below a partial pressure of 0.01 ATA.\2\ The Agency believes 
that this proposed condition would ensure proper compression and 
uniform distribution of the sorbent material in the cartridge, thereby 
preventing ``channeling'' in the material.\3\ By preventing channeling, 
the proposed condition would lower the diver's risk of rebreathing 
exhaled breathing gas that is high in CO2.
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    \2\ NOAA finds that physiological ``strain'' responses begin to 
develop with exposure to CO2 concentrations over 0.03 ATA 
(Ex. 3-12, p. 3-10). Therefore, OSHA believes that a threshold limit 
for CO2 of 0.01 ATA will provide divers with an adequate 
margin of protection from these effects.
    \3\ ``Channeling'' describes open spaces (or channels) that form 
in the sorbent material, and that permit exhaled breathing gas to 
pass through that part of the material to the inhalation side of the 
breathing apparatus with little or no absorption of the 
CO2 contained in the exhaled breathing gas. This 
condition typically results from failing to compress the sorbent 
material uniformly in the canister (e.g., by shaking the canister 
vigorously).
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    (j) Alternative to commercially pre-packed cartridges. Under this 
proposed condition, employers may fill CO2 scrubber 
cartridges manually instead of using commercially pre-packed 
cartridges. This practice would be acceptable if the employer meets all 
of the following conditions: The rebreather manufacturer permits 
employers to use this alternative method; the employer implements the 
alternative method according to the rebreather manufacturer's 
instructions; and the employer can demonstrate that the alternative 
method meets the performance requirements for commercially pre-packed 
cartridges specified by proposed Conditions 1(h) and 1(i). Therefore, 
the employer must be able to demonstrate to an OSHA compliance officer 
during an inspection that the manually filled cartridges are at least 
as effective as commercially pre-packed cartridges in removing 
CO2 from the breathing loop. The Agency believes that 
employers can obtain information regarding the effectiveness of 
manually filled and pre-packed cartridges from the rebreather 
manufacturers.
    (k) Information module. Condition 1(k) specifies that employers 
must ensure that their divers use an information module that provides 
them with critical dive information regarding electrical functions, gas 
pressures, and water temperature. For all rebreathers, the module must 
contain visual or auditory warning devices that would alert the diver 
to electrical weaknesses or failures (e.g., solenoid failure, low 
battery levels). In addition, modules used in semi-closed circuit 
rebreathers must contain visual displays for the partial pressure of 
CO2, or deviations above and below a preset CO2 
partial pressure of 0.005 ATA. For closed-circuit rebreathers, the 
module also must have visual displays for the partial pressures of 
O2 and CO2, or deviations above and below a 
preset CO2 partial pressure of 0.005 ATA and a preset 
O2 partial pressure of 1.40 ATA, plus a visual display for 
both gas temperature in the breathing loop and water temperature (see 
the discussion of water- and gas-temperature sensors under proposed 
Condition (2)(a) below). Warning divers of electrical weaknesses and 
failures would alert them that they should stop relying on their 
electrically operated equipment, especially sensors, and take 
protective actions. Providing information about O2 and 
CO2 partial pressures will alert divers to toxic levels of 
these gases in time for them to prevent extended exposure.
    While employers could provide recreational diving instructors and 
diving guides with dive-decompression computers for these purposes, 
OSHA believes that such computers are unnecessary because the divers 
would be diving within no-decompression limits, and the technical 
capability of dive-decompression computers far exceeds what is needed 
for no-decompression dives.
    (l) Checking electrical power and circuits. As noted above for 
proposed Condition 1(k), the information module must warn divers of low 
battery voltage when they are operating either semi-closed-circuit and 
closed-circuit rebreathers. In this regard, a partial or total 
electronic failure could interfere with sensor and control systems and 
have serious safety consequences for the diver. Therefore, OSHA 
believes that the diver's safety depends on properly operating 
electrical power supplies and electrical and electronic circuits. 
Accordingly, the proposed alternative would require employers to ensure 
that the electrical power supplies and electrical and electronic 
circuits in each rebreather are operating as required by the rebreather 
manufacturer's instructions. The employer must check for proper 
operation prior to beginning diving operations each day, and more often 
when necessary.
2. Special Requirements for Closed-Circuit Rebreathers
    (a) Supply-pressure and temperature sensors. This proposed 
condition requires employers to ensure that closed-circuit rebreathers 
use supply-pressure sensors for the O2 and diluent gases 
(i.e., air or nitrogen), as well as continuously functioning sensors 
for detecting temperature in the inhalation side of the breathing loop 
and in the ambient water. Supply-pressure sensors

[[Page 1403]]

would inform divers of the remaining supply of breathing-gas 
ingredients (i.e., O2 and air or nitrogen), thereby 
preventing an unexpected loss of breathing gas during a dive; Low gas 
supplies would alert the divers to an unusually high consumption of 
breathing gas, indicating a possible problem with the rebreather. A gas 
loss also could increase the need for a diver to make a rapid (i.e., 
emergency) ascent to the surface during a dive, which could result in 
over-pressurization of the lungs associated with AGE.
    OSHA believes that temperature sensors improve diver safety. Water-
temperature sensors alert divers to the possibility of hypothermia. In 
addition, the efficiency of the CO2-sorbent material 
deteriorates with decreasing temperatures (see Reference (4), Section 
III below). Breathing-loop temperature sensors and water-temperature 
sensors allow divers to estimate the duration of their CO2-
sorbent material. When divers are able to estimate the duration of 
their CO2-sorbent material, they can judge how long they can 
continue diving even if their CO2 sensors malfunction.
    (b) O2 sensors. Under this proposed condition, employers 
must ensure that at least two O2 sensors are located in the 
inhalation side of the breathing loop, and that these O2 
sensors function continuously, are temperature compensated, and 
approved by the rebreather manufacturer. OSHA believes that this 
proposal would provide the divers with critical information regarding 
O2 levels in the breathing gas, thereby preventing 
O2 deficiency or O2 toxicity resulting, 
respectively, from low or high O2 levels in the breathing-
gas mixture. By assuring appropriate levels of O2, the 
proposed condition would minimize the need for emergency escape and, as 
a consequence, reduce the risk of developing AGE.
    (c) Calibrating O2 sensors. Proposed Condition 2(c) 
specifies that employers, before the start of each day's diving 
operations, and more often when necessary, must calibrate O2 
sensors as required by the sensor manufacturer's instructions. 
Therefore, before they place a rebreather in operation, employers must: 
(i) Ensure that the equipment and procedures used to perform the 
calibration are accurate to within 1% of the O2 fraction by 
volume; (ii) maintain the accuracy of the calibration equipment as 
required by the manufacturer of the equipment; (iii) ensure that the 
sensors are accurate to within 1% of the O2 fraction by 
volume; (iv) replace O2 sensors when they fail to meet the 
accuracy requirements specified above in proposed Condition 2(c)(iii); 
and (v) ensure that the replacement O2 sensors meet the 
accuracy requirements specified above in proposed Condition 2(c)(iii).
    As noted under proposed Condition 3 below, maintaining accurate 
O2 levels in the breathing loop is critical to a diver's 
safety and health. To assure effective operation of O2 
sensors for this purpose, the introduction to proposed Condition 2(c) 
would require the employer to assess the accuracy of O2 
sensors before the start of each day's diving operations, and more 
often when necessary. Such an approach is consistent with the usual and 
customary practices of the rebreather community (see Ex. 3-4, pp. 4-1 
through 4-13, and 14-2). In addition, the introduction proposes that 
the calibration procedures conform to the sensor manufacturer's 
instructions; this proposal would ensure that the sensors measure 
accurately the partial pressure of O2 in the breathing loop.
    Proposed Condition 2(c) would provide assurance that divers always 
have accurate information regarding the level of O2 in the 
breathing loop, thereby enabling them to take corrective action should 
the O2 level exceed the parameters proposed below in 
Condition 3 (e.g., decrease O2 concentration, switch to the 
``bail-out system'' and egress to the surface (see proposed Condition 7 
below)).\4\ Therefore, accurate information regarding the O2 
level is critical to preventing the central nervous system and 
pulmonary effects of O2 toxicity (see proposed Condition 3 
below for a detailed discussion of these effects).
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    \4\ Although low O2 levels are rare under nitrox 
breathing conditions, the sensors also would detect levels of 
O2 less than 22% by volume (see proposed Condition 3 
below).
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    In view of the harmful effects that can result from breathing high 
levels of O2, OSHA believes that O2 sensors and 
associated calibrating equipment and procedures need to be accurate to 
``within 1% of the O2 fraction by volume.'' Assuming that 
the O2 sensor and calibrating equipment-procedure each 
underestimate O2 at the maximum proposed rate of 1%, and 
that the diver is breathing a nitrox mix containing 40% O2 
by volume or an O2 partial pressure of 1.40 ATA (the maximum 
O2 concentrations permitted under proposed Condition 3 
below), the error would be +/-0.8% when the O2 gauge shows 
the O2 level in the breathing loop to be 40% by volume, or 
+/-0.028 ATA when it shows the O2 level to be 1.40 ATA. The 
Agency believes that this level of error is acceptable, and well within 
the O2 toxicity limits demonstrated by the available 
evidence (see proposed Condition 3 below). Therefore, this level of 
accuracy would provide an adequate safety margin for the divers to 
detect anomalous O2 concentrations, to attempt to identify 
the cause and adjust breathing-system controls, and to ascend to the 
surface when necessary.
    (d) Controlling O2 delivery. This proposed condition 
requires employers to ensure that closed-circuit rebreathers have: (i) 
A gas-controller package with electrically-operated solenoid 
O2-supply valves; (ii) a pressure-activated regulator with a 
second-stage diluent-gas addition valve; (iii) a manually-operated gas-
supply bypass valve to add O2 and diluent gas to the 
breathing loop; and (iv) separate O2 and diluent-gas 
cylinders to supply the breathing-gas mixture. Under this proposed 
condition, closed-circuit rebreathers must automatically inject 
O2 into the breathing loop to maintain the pre-established 
O2 partial pressure in the breathable gas, and automatically 
add diluent gas (i.e., nitrogen or air) through the regulator to 
compensate for decreases in gas volume during descent. The diver must 
also be able to control these functions manually using gas-supply 
bypass valves provided on the equipment. This equipment would maintain 
O2 levels in the breathable gas within the range of partial 
pressures specified by proposed Condition 3 below, thereby providing 
assurance that sufficient and reliable breathing-gas pressure are 
available to deliver breathable gas to the diver without adversely 
affecting the diver's breathing effort. By reducing the diver's 
breathing effort, these proposed conditions would reduce CO2 
accumulation caused by an increased rate of breathing and, in turn, 
would lower the risk of CO2 toxicity. In addition, by 
maintaining O2 in the breathing loop at pre-established 
levels, this proposal would ensure that divers conform to the pre-
established 24-hour single-exposure O2 limit selected under 
proposed Condition 4 below.
    Paragraph (iv) of proposed Condition 2 requires that employers use 
separate cylinders to provide the O2 and diluent gas in the 
breathing-gas mixture. This proposal would give the diver independent 
control of these breathing-gas components; such control could be 
automatic or manual, or some combination of these two modes.

3. O2 Concentration in the Breathing Gas

    Under this proposed condition, employers must ensure that the 
fraction of O2 in the nitrox breathing-gas mixture exceeds 
the fraction of O2 in compressed air (i.e., more than 22% by 
volume). For rebreathers, the fraction of O2 must never 
exceed an O2 partial

[[Page 1404]]

pressure of 1.40 ATA; and for open-circuit SCUBA, the O2 
fraction must never exceed 40% by volume or an O2 partial 
pressure of 1.40 ATA, whichever exposes divers to less O2. 
The proposed requirement that the fraction of O2 be more 
than 22% is consistent with the definition of nitrox breathing-gas 
mixtures, i.e., that they contain more O2 than air. 
Specifying upper limits for the O2 component in the nitrox 
breathing-gas mixture would prevent divers from developing 
O2 toxicity.
    The available evidence supports the Agency's conclusion that 
exposure to a maximum O2 level of 1.40 ATA (or 40% by volume 
for open-circuit SCUBA) would prevent O2 toxicity.\5\ 
Several previous studies found that no O2 toxicity developed 
while breathing 1.40 ATA of O2 for extended periods, but 
breathing 1.60 ATA of O2 for the same periods resulted in a 
significant increase in O2 toxicity (see Exs. 3-4 (pp. 3-5 
through 3-16, P-15 and P-16, and P-37 through P-43), 3-9, and 3-10). 
OSHA could find no studies showing that O2 toxicity 
developed when divers used O2 at the partial pressures and 
for the durations proposed in this rulemaking, although in one study, 
two divers developed pulmonary toxicity when exposed to 1.40 ATA of 
O2 for a total of 55 hours over a 3-day period (Ex. 3-4, p. 
3-9). However, such an exposure is far in excess of the maximum time 
limit that recreational divers would experience, or that the 
O2-exposure limits specified in the 2001 NOAA Diving Manual 
or 1995 DSAT \6\ report would permit (see discussion regarding proposed 
Condition 4(a) below).
---------------------------------------------------------------------------

    \5\ Excessive O2 can impair a diver's central nervous 
system, resulting in seizures (and, as a consequence, death by 
drowning); it also can damage to the lungs and compromised pulmonary 
function.
    \6\ ``DSAT'' is an acronym for ``Diving Science and 
Technology,'' the research component of the International 
Professional Association of Diving Instructors, Inc., a trade 
association representing recreational diving instructors.
---------------------------------------------------------------------------

4. Limiting O2 Partial Pressure and Diving Depth
    (a) Limiting O2 partial pressure. Proposed Condition 
4(a) identifies the procedures employers would use to prevent 
O2 toxicity. Accordingly, employers must: (i) Determine a 
diver's O2 exposure duration using the maximum partial-
pressure O2 exposure during the dive and the total dive time 
(i.e., from the time the diver leaves the surface until the diver 
returns to the surface); and (ii) using the diver's exposure duration, 
ensure that a diver exposed to partial pressures of O2 
between 0.60 and 1.40 ATA does not exceed the 24-hour single-exposure 
O2 limits specified by the 2001 NOAA Diving Manual (see 
Section III below, Reference (1), p. 3-23) or by the 1995 DSAT report 
entitled ``Enriched Air Operations and Resources Guide'' (see Section 
III below, Reference (2), p. 34).
    The risk of O2 toxicity increases with O2 
partial pressure (i.e., dive depth) and dive duration. Therefore, as 
required by proposed Condition 4(a)(i), employers must use both of 
these factors to determine O2 exposure durations.
    Proposed Condition 4(a)(ii) refers to 24-hour single-exposure 
O2 limits specified in the 2001 NOAA Diving Manual and the 
1995 DSAT report entitled ``Enriched Air Operations and Resources 
Guide.'' Both NOAA and DSAT developed their O2-exposure 
limits using models and theories extensively tested in the field for 
safety and efficacy. The recreational diving industry recognizes and 
uses both procedures, and, as OSHA noted in granting a permanent 
variance to Dixie, both procedures would afford divers adequate 
protection against O2 toxicity.
    Under proposed Condition 4(a), when the employer determines 
exposure durations and limits divers' exposures accordingly, the Agency 
believes that they will reduce the divers' risk of O2 
toxicity to the rate found among divers who breathe compressed air from 
open-circuit SCUBA during no-decompression dives.
    (b) Limiting diving depth. This proposed condition requires that 
employers limit the divers covered by this proposed alternative to a 
maximum depth of 130 fsw or to a maximum O2 partial pressure 
of 1.40 ATA, whichever exposes them to less O2; this 
proposed condition would apply regardless of the diving equipment they 
use. This proposed condition would impose an additional constraint on 
O2 exposure, further reducing the risk of O2 
toxicity. Moreover, the proposed condition would aid in preventing DCS 
by limiting the divers' nitrogen exposure; this limitation occurs 
because O2 displaces nitrogen in the volume of breathing gas 
available for use. Therefore, limiting nitrogen exposure and 
restricting diving depth to 130 fsw would reduce the risk of DCS and, 
consequently, the need for decompression chambers.
    Lowering the partial pressure of nitrogen in a diver's body fluids 
and tissues, especially in the central nervous system, also would 
decrease the risk of nitrogen narcosis. Nitrogen narcosis is an 
anesthetic condition that results when high partial pressures of 
nitrogen are present in central nervous system tissues; the condition 
can impair a diver's performance and, in severe cases can result in 
injury or death (see Section III below, Reference (1), p. 3-20).
5. Mixing and Analyzing the Breathing Gas
    (a) Mixing of breathing gas by the employer. Under this proposed 
condition, when employers prepare the breathing-gas mixture, they must: 
(i) Ensure that properly trained personnel mix nitrox breathing gases, 
and that nitrogen is the only inert gas used in the breathing-gas 
mixture; and (ii) ensure that they mix the appropriate breathing-gas 
mixture before delivering it to the breathing-gas cylinders, using the 
continuous-flow or partial-pressure mixing techniques specified in the 
2001 NOAA Diving Manual, or using a filter-membrane system. This 
provision would provide quality control over the mixing process, so 
that the breathing-gas mixture contains the correct proportions of 
O2 and diluent gas (i.e., air or nitrogen). It also limits 
the diluent gas to air or nitrogen because OSHA believes that not 
enough information is available on other inert diluent gases (e.g., 
helium, argon, neon, hydrogen) or on trimix (three gas) breathing-gas 
mixtures to ensure the health and safety of divers under the diving 
conditions specified by this proposal.
    This proposed condition also states a general requirement that 
mixing processes produce the proper proportions of O2 and 
diluent gas prior to filling the SCUBA cylinders; this requirement 
would provide assurance that the divers' breathing-gas mixtures are 
correct and safe for use. In addition, it specifies that employers must 
select from among several mixing techniques commonly used and accepted 
by the diving industry. These techniques include the use of a ``filter-
membrane system,'' a recently developed mixing technique that de-
nitrogenates air (i.e., removes nitrogen from air using a filter 
membrane).\7\ After reviewing the technical literature available for 
this mixing system, the Agency believes that filter-membrane systems, 
which are commercially available from several manufacturers, would 
reduce the hazards associated with producing high-O2 
breathing-gas mixtures (e.g., fire, explosion) because the proportion 
of O2

[[Page 1405]]

in these systems never exceeds 40% by volume.
---------------------------------------------------------------------------

    \7\ Filter-membrane systems produce nitrox breathing-gas 
mixtures in two steps: First, they route air through filters to 
remove hydrocarbons and other contaminants; then they pass the 
decontaminated air through membranes that transfer O2 
across the membrane fibers at higher rates than nitrogen (hence, 
``de-nitrogenating'' the air). As the rate of air flow across the 
membrane fibers increases, the resulting ratio of O2 to 
nitrogen also increases.
---------------------------------------------------------------------------

    (b) Analyzing O2. This proposed condition requires 
employers, before the start of each day's diving operations, to 
determine the O2 fraction of the breathing-gas mixture using 
an O2 analyzer. In doing so, they must: (i) Ensure that the 
O2 analyzer is accurate to within 1% of the O2 
fraction by volume; and (ii) maintain this accuracy as required by the 
manufacturer of the analyzer. These provisions would ensure that the 
proportions of O2 and diluent gas in the breathing-gas 
mixtures conform to pre-established levels of these gases, thereby 
ensuring that divers remain within the 24-hour single-exposure 
O2 limits under proposed Condition 4 above. The accuracy 
requirements specified by these provisions are consistent with the 
accuracy requirements for O2 found in other requirements of 
this proposal, and serve the same purpose described for these 
requirements (see the detailed discussion of these requirements in 
proposed Condition 2(c) above).
    (c) Commercially supplied breathing gas. When the breathing gas is 
a commercially supplied nitrox breathing-gas mixture, this proposed 
condition requires employers to ensure that the O2 is Grade 
A (also known as ``aviator's oxygen'') or Grade B (referred to as 
``medical-industrial oxygen''), and meets the specifications, including 
the purity requirements, found in the ANSI-Compressed Gas Association 
Commodity Specification for Air, G-7.1-1997. In addition, employers 
must ensure that the commercial supplier: (i) Determines the 
O2 fraction in the breathing-gas mixture using an analytic 
method that is accurate to within 1% of the O2 fraction by 
volume; (ii) makes this determination when the mixture is in the 
charged tank and after disconnecting the charged tank from the charging 
apparatus; (iii) documents the O2 fraction in the mixture; 
and (iv) provides the employer with a written certification of the 
O2 analysis.
    OSHA believes that many employers covered by this proposal purchase 
breathing-gas mixtures commercially. Specifying grades A and B for the 
O2 would ensure that divers use the purest O2 
with optimal moisture content in their nitrox breathing-gas mixtures, 
thereby preventing them from inhaling contaminants, including 
hydrocarbons, that are known safety hazards. In addition, the 
O2 would be at comfortable moisture levels, which would help 
maintain normal pulmonary function.
    The proposed condition also controls the O2 levels in 
the mixture by requiring that the accuracy of the method used to 
analyze O2 conforms to the tolerance limits specified above 
under proposed Condition 5(b). The commercial suppliers must analyze 
the breathing-gas mixture actually contained in the SCUBA cylinders to 
determine the fraction of O2 that the divers will breathe, 
unaffected by O2 in the storage banks used to fill the SCUBA 
cylinders. The employer must ensure that the supplier of the breathing-
gas mixture documents the O2 fraction contained in the 
cylinder mixture, and certifies these results in writing. The written 
certification serves as a measure of quality assurance, and provides 
employers with documentation that the breathing-gas mixture contains 
the required fraction of O2.
    (d) Using a compressor. When employers produce nitrox breathing-gas 
mixtures, before using a compressor in which the gas pressure in any 
system component exceeds 125 psi, this proposed condition requires them 
to do the following: (i) Have the compressor manufacturer certify in 
writing that the compressor is suitable for mixing high-pressure air 
with the highest O2 fraction used in the nitrox breathing-
gas mixture; (ii) ensure that the compressor is oil-less or oil-free 
and rated for O2 service unless the employer complies with 
the requirements of proposed Condition 5(e) below; and (iii) ensure 
that the compressor meets the requirements specified in paragraph 
(i)(1) and (i)(2) of Sec.  1910.430 whenever the highest O2 
fraction used in the mixing process exceeds 40% by volume. The purpose 
of these proposed conditions is to prevent O2 explosions 
during the mixing process, the risk of which increases when gas 
pressure in a system component exceeds 125 psi.
    The requirements of Condition 5(d) would provide quality assurance 
that the compressor is designed and built so that its components cannot 
serve as ignition sources that could cause an O2 explosion. 
However, if the compressors are not rated as oil-less or oil-free 
(i.e., oil is used to lubricate components), paragraph (ii) of this 
condition requires that the compressors comply with the provisions of 
Condition 5(e) below to prevent the lubricating oil from serving as an 
ignition source. Paragraph (iii) of this condition addresses cascading 
processes in which an employer takes O2 from storage banks 
that contain O2 concentrations higher than 40% by volume, 
and mixes it with diluent gas from separate cylinder banks. The mixed 
product is a final breathing-gas mixture that does not exceed 40% by 
volume as required above by proposed Condition 3. Equipment used for 
this purpose must comply with paragraphs (i)(1) and (i)(2) of Sec.  
1910.430 (``Oxygen safety''). These paragraphs require employers to use 
equipment designed for O2 service and to clean the equipment 
of flammable materials before such use. Together with the other 
provisions of this proposed condition, these equipment requirements 
would reduce the risk of an O2 explosion.
    (e) Oil-lubricated compressors. Before an employer produces nitrox 
breathing-gas mixtures using an oil-lubricated compressor to mix high-
pressure air with O2, and regardless of the gas pressure in 
any system component, this proposed condition requires that the 
employer: (i) Have the compressor manufacturer certify in writing that 
the compressor is suitable for mixing the high-pressure air with the 
highest O2 fraction used in the nitrox breathing-gas 
mixture; (ii) filter the high-pressure air to produce O2-
compatible air; (iii) have the filter-system manufacturer certify in 
writing that the filter system used for this purpose is suitable for 
producing O2-compatible air; (iv) continuously monitor the 
air downstream from the filter for hydrocarbon contamination; and (v) 
use only uncontaminated air (i.e., air containing no hydrocarbon 
particulates) for the nitrox breathing-gas mixture.
    Oil-based lubricants contain hydrocarbons that can ignite in the 
presence of an enriched O2 environment during the mixing 
process, causing an explosion that can injure or kill employees. OSHA 
believes that these proposed requirements would reduce this risk by 
ensuring that high-pressure O2 being pumped through the 
compressor remains isolated from the oil-based lubricant. Under the 
proposed conditions, the employer's actions will assure that the air 
used for the nitrox breathing-gas mixture is not contaminated, while 
the manufacturer's certification will provide assurance that the 
equipment will produce and filter this mixture safely. As an additional 
safety precaution, the monitoring requirement proposed under paragraph 
(v) would warn the employer that high-pressure O2 is mixing 
with the oil-based lubricant, and to take emergency action (e.g., shut 
off O2 flow to the compressor and then purge the compressor 
with an inert gas).
    (f) Compliance with other OSHA standards. Under this proposed 
condition, employers must ensure that SCUBA equipment using nitrox 
breathing-gas mixtures or pure O2 under high pressure (i.e., 
exceeding 125 psi) complies with the requirements specified by 
paragraphs (i)(1) and (i)(2) of Sec.  1910.430. This provision ensures

[[Page 1406]]

that this equipment is free of ignition sources that could cause an 
O2 explosion. As noted above in the discussion of proposed 
Condition 3(d)(iii), paragraphs (i)(1) and (i)(2) of Sec.  1910.430 
would reduce this risk by requiring employers to use diving equipment 
designed for O2 service and to clean the equipment of 
flammable materials before such use.\8\
---------------------------------------------------------------------------

    \8\ In addition, employers must comply with other OSHA standards 
that ensure accurate mixing and decontamination (especially 
hydrocarbon removal) of nitrox breathing gases, and that employees 
are protected properly during these activities. These standards 
include the appropriate provisions of Sec. Sec.  1910.101 
(``Compressed gas (general requirements)'') and 1910.169 (``Air 
receivers'').
---------------------------------------------------------------------------

6. Use of No-Decompression Limits
    (a) No-decompression procedures. Under this proposed condition, 
employers must ensure that divers using nitrox breathing-gas mixtures 
remain within the no-decompression limits specified for single and 
repetitive air diving and published in the 2001 NOAA Diving Manual (see 
Section III below, Reference (1)) or the 1994 DSAT report entitled 
``Development and Validation of No-Stop Decompression Procedures for 
Recreational Diving: The DSAT Recreational Dive Planner'' (see Section 
III below, Reference (3)). This proposed condition allows employers to 
use the no-decompression limits published in the 2001 NOAA Diving 
Manual or the 1994 DSAT no-decompression tables. OSHA intends to ensure 
that the divers using nitrox mixtures under the proposed alternative 
receive the same protection against DCS as is afforded to divers who 
use air. For this reason, the proposed condition requires that 
employers ensure that their divers never exceed the no-decompression 
limits published in either the 2001 NOAA Diving Manual or 1994 DSAT 
report; in determining these limits, employers must use the partial 
pressure of nitrogen in the nitrox breathing-gas mixture to derive the 
equivalent air depth for a specific dive duration (see Ex. 3-12, p. 15-
7).
    OSHA believes that by adopting these no-decompression limits, the 
proposed alternative would protect recreational diving instructors and 
diving guides at least as well as the use of compressed air supplied to 
open-circuit SCUBAs under no-decompression diving limits. The 1994 DSAT 
no-decompression limits have been determined to be reliable and valid, 
based on extensive laboratory and field testing, and have been widely 
accepted by both the diving and scientific communities (see Appendix E 
(``Comment and critique from the field'') of the 1994 DSAT report).
    In determining its no-decompression limits for nitrox breathing-gas 
mixtures in its 2001 Diving Manual, NOAA applies the equivalent-air-
depth (``EAD'') formula. Divers using nitrox breathing-gas mixtures can 
use the EAD formula to determine accurately the no-decompression limits 
for different nitrogen partial pressures. NOAA applies its EAD formula 
in determining what equivalent air decompression limits to use with 
nitrox breathing-gas mixtures. The formula assumes that equivalent 
nitrogen partial pressures and dive durations will result in similar 
DCS risk to dives performed with air. OSHA believes that the NOAA EAD 
formula can accurately estimate the DCS risk associated with nitrox 
breathing-gas mixtures based on equivalent nitrogen partial pressures 
and dive durations used in air diving. In the record granting a 
permanent variance to Dixie, OSHA received evidence addressing the 
safety and efficacy of the EAD formula from Dr. Edward D. Thalmann (Ex. 
2-7). Dr. Thalmann is a world-renowned expert in treating diving-
related medical emergencies among recreational divers; he is also the 
author of a number of scientific publications that address the causes 
and treatment of diving-related medical emergencies, especially DCS. 
Based on this research and his field experience, Dr. Thalmann stated 
that DCS associated with breathing a nitrox gas mixture ``should not be 
substantially different in incidence and severity compared to diving on 
air[,] provided the [n]itrox no-decompression times are computed from 
accepted air no-decompression limits using the [NOAA] EAD [formula].'' 
Dr. Thalmann concluded that, within these constraints, ``there is no 
rationale for having different requirements for * * * air and [n]itrox 
no-decompression diving.'' Based on Dr. Thalmann's comments, OSHA 
concludes that NOAA's EAD formula will translate accurately the partial 
pressure of nitrogen in a nitrox breathing-gas mixture to an equivalent 
air depth for a specific dive duration, and that employers can rely on 
this formula to determine safe no-decompression limits for their divers 
based on the equivalent air dives.
    (b) Dive-decompression computers. This proposed condition permits 
employers to use dive-decompression computers designed to regulate 
decompression when the computers use the NOAA or DSAT no-decompression 
limits specified in proposed Condition 6(a) and provide output that 
reliably represents these limits. OSHA believes that dive-decompression 
computers are unnecessary because the divers would be diving within no-
decompression limits, and the technical capability of most dive-
decompression computers exceeds the requirements of no-decompression 
dives. Nevertheless, the proposal would allow employers the flexibility 
to use either manual calculations or dive-decompression computers to 
determine the no-decompression schedules, with the use of dive-
decompression computers for this purpose being optional. However, when 
employers choose to use these computers, they also must provide their 
diver with specific decompression information, and have a hard-copy of 
the appropriate decompression tables at the dive site (see proposed 
Condition 9(c) below). Thus, the proposal specifies the conditions that 
employers must meet to ensure that their employees' diving activities 
conform to accepted no-decompression practices, whether or not they use 
dive-decompression computers.
    The Agency finds that restricting the no-decompression limits 
programmed into the computers to those limits published by the 2001 
NOAA Diving Manual and the 1994 DSAT report would prevent employers 
from using the computers to provide alternate no-decompression limits 
that could place divers at higher risk for DCS. Operating under this 
constraint, OSHA concludes that computers may provide an advantage over 
manual calculations because manual calculations are subject to human 
error, and computers may reduce such error.
7. Emergency Egress
    (a) Bail-out system for all SCUBAs. For emergencies involving SCUBA 
malfunctions that could endanger diver health and safety (e.g., high 
CO2 levels), proposed Condition 7(a) requires employers to 
equip their divers with a reliable emergency-egress system (i.e., a 
``bail-out system''). The bail-out system would contain a separate 
supply of breathing gas, which can include air. In addition, the bail-
out system would provide the breathing gas to the second stage of the 
SCUBA regulator. Accordingly, the proposed bail-out system would 
provide divers with the capability to shift to a known, safe, and 
immediately available breathing gas, and to terminate the dive safely 
whenever a CO2-related problem or other emergency occurs.
    (b) Alternative bail-out system for open-circuit SCUBA. The 
proposal would provide an alternative to the bail-out for divers using 
open-circuit SCUBA. Accordingly, when open-

[[Page 1407]]

circuit SCUBA provides the nitrox breathing-gas mixture, the proposal 
would permit employers to use the emergency-egress procedure (i.e., a 
reserve breathing-gas supply) specified for open-circuit SCUBA by 
paragraph (c)(4)(i) of Sec.  1910.424 instead of a separate bail-out 
breathing-gas system.
    Paragraph (c)(4)(i) of Sec.  1910.424 is an emergency-escape 
provision in OSHA's existing CDO standards that applies to divers who 
use air-supplied open-circuit SCUBA. Under this provision, employers 
can maintain a reserve supply of breathing-gas in the breathing-gas 
cylinders carried by the diver, and that the diver can access in an 
emergency by manually activating a J valve located on the supply 
manifold. Having already recognized the safety afforded to divers by 
this system in the context of air-supplied, open-circuit SCUBA diving, 
the Agency believes that it would provide a similar level of protection 
to divers who use open-circuit SCUBA supplied with nitrox breathing-gas 
mixtures.
    (c) Safety requirements. This proposed condition requires employers 
to provide their divers with a system that performs reliably and 
supplies sufficient emergency breathing gas to enable the diver to 
terminate the dive and return safely to the surface. Accordingly, this 
proposed requirement would ensure that the bail-out system used by 
employees, whether it is an independent or integrated bail-out system, 
will function appropriately when needed by the diver for emergency 
egress. The bail-out system must enable the diver to terminate the dive 
and make a safe and orderly ascent to the surface under ``worst-case'' 
conditions, thereby preventing over-pressurization of the lungs 
associated with AGE. However, OSHA is not proposing a specific capacity 
for bail-out systems because it believes that the SCUBA manufacturers 
are in the best position to make this determination. In this regard, a 
rebreather manufacturer could determine the capacity that is needed for 
the bail-out system based on critical diving parameters (e.g., depth of 
dive and breathing rate) provided by the employer.
8. Treating Diving-Related Medical Emergencies
    (a) Availability of medical resources. This proposed condition 
requires that employers, prior to beginning diving operations each day, 
ensure that: (i) A hospital, qualified health-care professionals, and 
the nearest Coast Guard Coordination Center (or an equivalent rescue 
service operated by a State, county, or municipal agency) are available 
for diving-related medical emergencies; (ii) each dive site has a means 
to alert these treatment resources in a timely manner when a diving-
related medical emergency occurs; and (iii) transportation to a 
suitable decompression chamber is readily available when no 
decompression chamber is at the dive site, and that this transportation 
can deliver the injured diver to the decompression chamber within two 
hours travel time from the dive site. Overall, the proposed provisions 
would avoid unnecessary delay in treating diving-related injuries by 
confirming that resources are on call and available to render 
appropriate treatment, by alerting them to the occurrence of a diving-
related medical injury so they can initiate treatment action (e.g., 
using a pre-programmed electronic system, list of telephone numbers), 
and by providing timely transportation for the injured diver to the 
treatment facility. OSHA believes that reducing treatment delay will 
improve the likelihood that an injured diver will recuperate fully from 
any diving-related injury.
    Prior to granting the permanent variance to Dixie, OSHA requested 
Dr. Edward D. Thalmann to render an opinion on the likely incidence of 
AGE and DCS under the proposed variance conditions. In doing so, Dr. 
Thalmann reviewed available research studies, as well as data from the 
Diver Alert Network (``DAN'') (Ex. 2-7). With regard to AGE, Dr. 
Thalmann stated, ``[AGE] is a rare occurrence and can be avoided with 
proper training and experience,'' that it ``is essentially independent 
of the time at depth,'' and that ``there is no evidence * * * [to] 
suggest that the occurrence and outcome of [AGE] would be any different 
breathing a [n]itrox mixture [other] than air.'' In addressing DCS, Dr. 
Thalmann noted that DCS associated with breathing a nitrox gas mixture 
``should not be substantially different in incidence and severity 
compared to diving on air[,] provided the [n]itrox no-decompression 
times are computed from accepted air no-decompression limits using the 
[NOAA] EAD [formula].''
    Dr. Thalmann then discussed the two-hour transportation limit 
proposed for the Dixie variance by reviewing the available DAN data; he 
cautioned that these data ``apply to recreational diving only where the 
vast majority of diving is within no-decompression limits.'' Under 
these conditions, he found that for both pain-only DCS and DCS with 
severe neurological symptoms, a treatment delay of four hours can occur 
without diminishing treatment success (i.e., complete relief of 
symptoms). In summary, Dr. Thalmann stated, ``There is no significant 
body of evidence to suggest that, so long as one is diving within 
accepted no-decompression limits breathing air or [n]itrox, having 
access to a recompression facility within 4 hours is inadequate.'' For 
the reasons set forth in Dr. Thalmann's expert opinion, OSHA believes 
that the proposed condition for availability of medical treatment would 
provide adequate employee safety.
    (b) O2 treatment. Oxygen treatment is the preferred 
means of initially treating AGE and DCS (see Section III below, 
Reference (1), pp. 3-19 and 3-28). This proposed condition would 
require the employer to ensure that portable O2 equipment is 
available at the dive site to treat an injured diver. This equipment 
must deliver pure O2 to a transparent mask that covers the 
injured diver's nose and mouth. To provide assurance that the 
O2 is suitable for treatment purposes, this proposed 
condition also requires employers to use only O2 that meets 
the criteria for Medical USP oxygen (Type I, Quality Verification Level 
A) of CGA G-4.3-2000 (``Commodity Specification for Oxygen''). 
Additionally, sufficient O2 must be available to administer 
to the injured diver from the time the employer recognizes the symptoms 
of a diving-related medical emergency until the injured diver reaches a 
decompression chamber for treatment. This proposed condition would 
require that the O2 supplied for this purpose be pure 
O2, and that the injured diver receive the O2 
continuously from the time an employer detects the diving-related 
medical emergency until the diver begins treatment in a decompression 
chamber. These provisions would ensure that injured divers receive the 
maximum dose of O2 possible to enhance treatment 
effectiveness. The transparent mask covering the diver's nose and mouth 
allows attendants to monitor the diver's breathing and provides an 
effective seal against O2 loss.
    (c) Treatment personnel. This proposed condition requires the 
employer to ensure that at least two attendants (either employees or 
non-employees) qualified in first-aid and administering O2 
treatment are available at the dive site to treat diving-related 
medical emergencies before starting each day's diving operations, and 
to verify their qualifications before using them for this purpose. 
Under these proposed requirements, only qualified personnel would 
administer initial treatment to injured divers. OSHA believes that 
personnel qualified in first aid and O2 treatment would 
stabilize the

[[Page 1408]]

injured diver as rapidly as possible, thereby improving the 
effectiveness of subsequent treatment regimens. Regarding the use of 
non-employees, the Agency notes that the main purpose of the proposed 
condition is to ensure that properly qualified personnel are available 
for initial treatment, regardless of their employment status. However, 
recognizing that the employer may not be familiar with the 
qualifications of the non-employee involved in this procedure, OSHA is 
proposing that employers verify their qualifications prior to using 
them for this purpose.
9. Diving Logs and Decompression Tables
    (a) Diving log. This proposed condition requires employers, before 
beginning diving operations, to (i) designate an employee or non-
employee to make entries in a diving log, and (ii) verify that this 
designee understands the diving and medical terminology, as well as the 
proper procedures, for making such entries. Recognizing that many 
employers of recreational divers and diving guides are small businesses 
that may have difficulty finding an employee to make entries in the 
diving log, OSHA is proposing to allow non-employees to make entries in 
the log. The Agency believes that any properly qualified individual can 
make such entries, provided the employer verifies their qualifications 
before using them for this purpose; these qualifications include an 
understanding of the diving and medical terminology and established 
procedures needed to enter the required information accurately in a 
diving log.
    (b) Diving log requirements. Proposed Condition 9(b) specifies that 
employers must: (i) Ensure that diving logs meet the information 
requirements specified by Sec.  1910.423(d), including the requirement 
for DCS information when appropriate; and (ii) maintain diving logs in 
accordance with the provisions of Sec.  1910.440, including the 
requirements for record availability, access to records by employees 
and OSHA, and retention of records. Employers covered by this proposal 
already are required to comply with these provisions because their 
employees breathe a mixed gas (i.e., nitrox) during diving operations; 
this proposed paragraph merely emphasizes this important obligation. In 
addition, during inspections, OSHA intends to review these records to 
determine whether the procedures proposed in this rulemaking are 
providing adequate protection to recreational diving instructors and 
diving guides.
    (c) Availability of decompression tables. This proposed condition 
requires employers to have a hard-copy of the no-decompression tables 
used for the dives (see proposed Condition 6(a) above) readily 
available at the dive site, whether or not the divers use dive-
decompression computers. This condition would ensure that the 
parameters of the no-decompression limits are readily available and 
accessible as a reference source. In addition, a hard-copy of the 
decompression tables would serve both as a reference source should 
decompression become necessary, and as a back-up resource to divers 
with dive-decompression computers.
10. Diver Training
    Under proposed Condition 10, employers must ensure that their 
divers receive training that enables them to perform their work safely 
and effectively while using open-circuit SCUBAs or rebreathers supplied 
with nitrox breathing-gas mixtures. Training would include the 
following areas: Recognizing the effects of breathing excessive 
CO2 and O2; taking appropriate action after 
detecting the effects of breathing excessive CO2 and 
O2; and properly evaluating, operating, and maintaining 
their diving equipment under the diving conditions they encounter. OSHA 
believes that such training would provide divers with the basic skills 
and knowledge necessary to ensure that diving is performed safely.
    The proposed provision is performance-based, requiring employers to 
ensure that their employees are trained to perform safely and 
effectively while using open-circuit SCUBAs or rebreathers supplied 
with nitrox breathing-gas mixtures. In this regard, the Agency believes 
that employers are in the best position to determine when the training 
that their divers obtain is adequate to perform their jobs safely and 
effectively. However, the provision specifies several critical tasks 
that the recreational diving instructors and diving guides would have 
to perform safely and effectively, including detecting and managing 
excessive levels of CO2 and O2, and being able to 
evaluate, operate, and maintain their diving equipment. Such training 
would enable divers to take remedial action to prevent and escape the 
life-threatening effects of CO2 and O2 toxicity, 
including convulsions and loss of consciousness. In addition, OSHA 
believes that divers who know how to evaluate, operate, and maintain 
their open-circuit SCUBAs and rebreathers under the diving conditions 
they encounter will be less likely to require emergency egress because 
of equipment failure, thereby reducing the incidence of AGE from rapid 
ascents to the surface.
11. Testing Protocol for Determining the CO2 Limits of 
Rebreather Canisters
    This proposed condition specifies the requirements employers must 
follow when they use a schedule to replace depleted CO2-
sorbent material instead of using CO2 sensors to detect when 
the material is no longer absorbing CO2 effectively (see 
proposed Condition 1(h) above). Employers may use a CO2-
sorbent replacement schedule developed by a rebreather manufacturer 
only when the manufacturer has tested the canisters according to the 
proposed canister-testing protocol in Appendix C. The Agency adapted 
this protocol from the canister-testing parameters and statistical 
procedures developed by the U.S. Navy Experimental Diving Unit 
(``NEDU'') (see, respectively, Ex. 3-11 and Reference (4), Section III 
below); the NEDU is the only Federal agency involved in testing 
CO2-sorbent replacement schedules. OSHA believes that the 
NEDU protocol provides valid and reliable data for determining 
CO2-sorbent replacement schedules because they are carefully 
executed and control significant variables that deplete CO2-
sorbent materials, such as breathing rate (by using breathing machines) 
and ambient temperature.
    (a) Quality-control assessment of CO2-sorbent material. 
Under this proposed condition, employers must use CO2-
sorbent materials in rebreathers that have the necessary physical 
properties as determined by the following procedures: (i) The NATO 
CO2 absorbent-activity test to assess the capacity of the 
material to absorb CO2; (ii) the RoTap shaker and nested 
sieves to determine granule-size distribution; (iii) the NEDU-derived 
Schlegel test to assess the friability of the CO2-sorbent 
material; and (iv) the NEDU's MeshFit software to evaluate mesh size 
conformance to specifications. These procedures would provide a 
quality-control assessment of CO2-sorbent materials. By 
ensuring that these materials meet the physical criteria established by 
these procedures, employers would improve the reliability with which 
they estimate canister durations during diving operations; improved 
estimates would enable divers to replace CO2-sorbent 
material before it fails (i.e., before CO2 increases to 
dangerous levels).
    (b) Testing canister function. This proposed condition requires 
employers to provide divers with canisters for their rebreathers that 
have been tested using a protocol consisting of specified canister-
testing methods, procedures,

[[Page 1409]]

and statistical analyses. This proposed canister-testing protocol 
measures the performance effects on canisters of the following three 
factors: Depth, exercise level (i.e., ventilation rate), and water 
temperature. Depth is the maximum depth at which a diver would use the 
CO2-sorbent material, which for this proposed amendment is 
130 fsw. For the other variables, OSHA has selected three combinations 
of ventilation rates and CO2-injection rates from the NEDU 
protocol to simulate three diverse levels of exercise (light, moderate, 
and heavy). The four water temperatures used in the proposed protocol 
are 40, 50, 70, and 90 degrees F (4.4, 10.0, 21.1, and 32.2 degrees C, 
respectively); these temperatures represent the wide range of water 
temperatures that recreational diving instructors and diving guides are 
likely to encounter.
    For this application, the Agency has revised the NEDU protocol 
slightly by: Limiting the maximum depth to 130 fsw; requiring an 
O2 fraction of 0.28 in the nitrox breathing-gas mixture 
(this fraction being the maximum O2 concentration permitted 
at this depth by this proposal); providing tolerance limits for water 
temperatures; and defining canister duration as the time taken to reach 
0.005 ATA of CO2 (0.005 ATA of CO2 is the level 
specified in this proposal as the maximum allowable amount of 
CO2 in the breathing gas). In addition, the proposed 
protocol expressly prohibits the use of CO2-sorbent 
replacement schedules based on extrapolation of the protocol results. 
NEDU's statistical procedures (see Section III below, Reference (4)) do 
not provide a method for extrapolating the duration of CO2-
sorbent materials beyond the results obtained during the canister-
testing trials. Accordingly, the proposed canister-testing protocol 
provides improved validity and reliability of canister-replacement 
schedules, and will enable employers to replace CO2-sorbent 
materials in a timely manner.

III. References

    The preamble to this proposal cites the following references:
    (1) National Oceanic and Atmospheric Administration (2001). NOAA 
Diving Manual: Diving for Science and Technology. Joiner, J. T. (ed.). 
Best Publishing Co., Flagstaff, AZ. (Ex. 3-12.)
    (2) Diving Science and Technology (1995). ``Analysis of Proposed 
Oxygen Exposure Limits for DSAT Oxygen Exposure Table Against Existing 
Database of Manned Oxygen Test Dives.'' Enriched Air Operations and 
Resource Guide. International PADI, Inc., Rancho Santa Margarita, 
California. (Ex. 3-13.)
    (3) R. W. Hamilton, R. E. Rogers, M. R. Powell, and R. D. Vann 
(1994). ``Development and Validation of No-Stop Decompression 
Procedures for Recreational Diving: The DSAT Recreational Dive 
Planner.'' Hamilton Research, Ltd., Tarrytown, New York. (Ex. 3-14.)
    (4) J. R. Clarke. ``Statistically Based CO2 Canister 
Duration Limits for Closed-Circuit Underwater Breathing Apparatus.'' 
U.S. Navy Experimental Diving Unit, Report 2-99, 1999. (Ex. 2-9.)
    Copies of these references are available from the OSHA's Docket 
Office, Room N-2625, U.S. Department of Labor, 200 Constitution Avenue, 
NW., Washington, DC 20210; telephone (202) 693-2350 or fax (202) 693-
1648.

IV. Legal Considerations

    Employers covered by this proposal currently are covered by OSHA's 
Commercial Diving Operations (CDO) standards at 29 CFR 1910, subpart T. 
The requirements of these standards are protecting their employees from 
significant risk. In issuing the variance from this standard, the 
Agency determined that the practices and protections in the variance 
would provide recreational diving instructors and diving guides with 
comparable protection to that provided by the CDO standards. The 
present proposal would extend these alternative protections to all such 
instructors and guides. In this regard, the proposed amendment would 
not replace existing requirements, but instead would be a limited 
alternative to them. Therefore, OSHA finds that the proposed amendment 
would not directly increase or decrease the protection afforded to 
employees, nor would it increase employers' compliance burdens. As 
demonstrated in the following sections, the proposed revision likely 
would reduce employers' compliance burdens by eliminating the 
requirement to have a decompression chamber at the dive site when they 
comply with the conditions specified in the proposed amendment.

V. Preliminary Economic Analysis and Regulatory Flexibility 
Certification

    The proposed amendment is not a significant rulemaking under 
Executive Order 12866, or a ``major rule'' under the Unfunded Mandates 
Reform Act or Section 801 of the Small Business Regulatory Enforcement 
Fairness Act (SBREFA). The proposal would impose no additional costs on 
any private or public sector entity, and does not meet any of the 
criteria for a significant or major rule specified by the Executive 
Order or relevant statutes.
    OSHA believes that the proposed amendment likely would offer 
employers of recreational diving instructors and diving guides an 
opportunity to expand these services into nitrox diving operations by 
eliminating costs associated with purchasing and maintaining a 
decompression chamber at the dive site when they comply with the 
conditions specified in the proposed amendment. By providing regulatory 
flexibility to these employers, the proposal may reduce their costs and 
increase productive time. Therefore, the Agency concludes that the 
proposed amendment would not impose any additional costs on these 
employers; consequently, the proposal requires no preliminary economic 
analysis. Furthermore, because the proposal imposes no costs on 
employers, OSHA certifies that it would not have a significant impact 
on a substantial number of small businesses; accordingly, the Agency 
need not prepare an initial regulatory flexibility analysis.

VI. Paperwork Reduction Act

    After a thorough analysis of the proposal, OSHA believes that it 
contains the following two collection-of-information (i.e., paperwork) 
requirements: Conditions 9(b)(i) and 9(b)(ii) of proposed Appendix C. 
Condition 9(b)(i) requires employers to ensure that the diving log 
conforms to the requirements specified by paragraph (d) (``Record of 
dive'') of Sec.  1910.423, while Condition 9(b)(ii) specifies that 
employers must keep a record of the dive in accordance with Sec.  
1910.440 (``Recordkeeping requirements''). However, these paperwork 
requirements already apply to these employers under subpart T, 
regardless of this proposal, because their divers are using a mixed 
(i.e., nitrox) gas breathing supply. The regulatory alternative in this 
proposed rulemaking only exempts the covered employers from having to 
maintain decompression chambers at the dive site, and does not exempt 
them from the other provisions of subpart T that apply to mixed-gas 
diving operations. Accordingly, the Agency already incorporates the 
time and cost burdens associated with these two paperwork requirements 
under Control No. 1218-0069.
    Interested parties who wish to comment on OSHA's determination that 
this proposal contains no additional paperwork requirements must send 
their written comments to the Office of Information and Regulatory 
Affairs,

[[Page 1410]]

Attn: OMB Desk Officer for OSHA, Office of Management and Budget, Room 
10235, 726 Jackson Place, NW., Washington, DC 20503. The Agency also 
encourages commenters to submit their comments on this paperwork 
determination to OSHA along with their other comments on the proposed 
rule.

VII. Federalism

    The Agency has reviewed the proposed amendment to its Commercial 
Diving Operations standards according to the most recent Executive 
Order on Federalism (Executive Order 13132, 64 FR 43225, August 10, 
1999). This Executive Order requires that Federal agencies, to the 
extent possible, refrain from limiting State policy options, consult 
with States before taking actions that restrict their policy options, 
and take such actions only when clear constitutional authority exists 
and the problem is of national scope. The Executive Order allows 
Federal agencies to preempt State law only with the expressed consent 
of Congress; in such cases, Federal agencies must limit preemption of 
State law to the extent possible.
    Under section 18 of the OSH Act, Congress expressly provides OSHA 
with authority to preempt State occupational safety and health 
standards to the extent that the Agency promulgates a Federal standard 
under section 6 of the OSH Act. Accordingly, section 18 of the OSH Act 
authorizes the Agency to preempt State promulgation and enforcement of 
requirements dealing with occupational safety and health issues covered 
by OSHA standards unless the State has an OSHA-approved occupational 
safety and health plan (i.e., is a State-plan State). (See Gade v. 
National Solid Wastes Management Association, 112 S. Ct. 2374 (1992).) 
Therefore, with respect to States that do not have OSHA-approved plans, 
the Agency concludes that this proposal conforms to the preemption 
provisions of the OSH Act. Additionally, section 18 of the OSH Act 
prohibits States without approved plans from issuing citations for 
violations of OSHA standards; the Agency finds that the proposed 
rulemaking does not expand this limitation.
    OSHA has authority under Executive Order 13132 to propose this 
amendment to its Commercial Diving Operations standards because the 
problems addressed by these requirements are national in scope. In this 
regard, the proposed amendment offers thousands of employers across the 
nation whose divers provide recreational diving instruction and dive-
guiding services an opportunity to expand these services into nitrox 
diving operations, and to do so without the expense involved in 
purchasing a decompression chamber. The proposed amendment would 
provide employers in every State with alternative means of compliance 
to protect their recreational diving instructors and diving guides from 
the risks of decompression sickness and arterial gas embolism while 
using a breathing-gas mixture consisting of a high percentage of oxygen 
mixed with nitrogen supplied by an open-circuit, semi-closed-circuit, 
or closed-circuit self-contained breathing apparatus.
    Section 18(c)(2) of the OSH Act (29 U.S.C. 667(c)(2)) requires 
State-plan States to adopt OSHA standards, or develop alternatives, 
that are at least as effective as the OSHA amendment. The States have 
already adopted OSHA's Commercial Diving Operations (CDO) standards at 
29 CFR 1910, subpart T, in particular, the decompression chamber 
provisions of paragraphs (b)(2) and (c)(3)(iii) of Sec.  1910.423(b)(2) 
and paragraph (b)(1) of Sec.  1910.426(b)(1). Compliance with the 
proposed amendment would only provide employers with an alternative to 
the requirements of the CDO standards; therefore, the alternative is 
not, itself, a mandatory standard. Accordingly, State-plan States are 
not obligated to adopt the final amendment that results from this 
rulemaking. Nevertheless, OSHA strongly encourages them to adopt to the 
final amendment to provide compliance options to employers in their 
States.

VIII. State Plans

    The Agency strongly encourages the 23 States and two Territories 
with their own OSHA-approved occupational safety and health plans to 
revise their current Commercial Diving Operations standards when the 
Agency publishes the final amendment that results from this rulemaking. 
OSHA believes that such a revision would provide employers in the 
State-plan States the economic benefits that are likely to accrue from 
its enactment, while protecting the safety and health of recreational 
diving instructors and diving guides. These States and Territories are: 
Alaska, Arizona, California, Connecticut, New York (for State and local 
government employees only), Hawaii, Indiana, Iowa, Kentucky, Maryland, 
Michigan, Minnesota, Nevada, New Mexico, North Carolina, Oregon, Puerto 
Rico, South Carolina, Tennessee, Utah, Vermont, Virginia, Virgin 
Islands, Washington, and Wyoming.

IX. Unfunded Mandates

    OSHA reviewed the proposed amendment according to the Unfunded 
Mandates Reform Act of 1995 (UMRA) (2 U.S.C. 1501 et seq.) and 
Executive Order 12875. As discussed above in section V (``Preliminary 
Economic Analysis and Regulatory Flexibility Certification'') of this 
preamble, the Agency has made a preliminary determination that the 
proposed amendment imposes no additional costs on any private or public 
sector entity. The substantive content of the proposed amendment 
applies only to employers of recreational diving instructors and diving 
guides, and compliance with the proposed amendment would be strictly 
optional for the employers. Accordingly, the proposed amendment would 
require no additional expenditures by either public or private 
employers.
    OSHA standards do not apply to State and local governments, except 
in States that have voluntarily elected to adopt a State plan approved 
by the Agency. Consequently, the proposed amendment does not meet the 
definition of a ``federal intergovernmental mandate'' (see section 
421(5) of the UMRA (2 U.S.C. 658(5)). In conclusion, the proposed 
amendment does not mandate that State, local, and tribal governments 
adopt new, unfunded regulatory obligations.

X. Applicability of Existing Consensus Standards

    OSHA is not aware of any national consensus standards that are 
similar to the amendment that it is proposing in this rulemaking.

XI. Public Participation

    The Agency requests members of the public to submit written 
comments and other information concerning this proposal. These comments 
may include objections to the proposal with or without a hearing 
request, as well as comments that endorse or support the proposed 
amendment set forth in this notice. OSHA welcomes such comments and 
information so that the record of this rulemaking will represent a 
balanced public response on the issues involved. See the sections above 
titled DATES and ADDRESSES for information on submitting these comments 
and information to the Agency. Submissions received within the 
specified comment period will become part of the record, and will be 
available for public inspection and copying in the OSHA Docket Office.
    Under section 6(b)(3) of the OSH Act and 29 CFR 1911.11, members of 
the public may request an informal hearing by following the 
instructions under the section of this Federal Register notice titled 
Addresses. These requests must include the objections to the proposal

[[Page 1411]]

that warrant a hearing. The party making objections that are part of a 
hearing request must:
    [sbull] Include their name and address.
    [sbull] Ensure that the request is sent or postmarked no later than 
April 10, 2003.
    [sbull] Separately number each objection.
    [sbull] Specify with particularity the grounds for each objection.
    [sbull] Include a detailed summary of the evidence supporting each 
objection which they plan to offer at the requested hearing.

List of Subjects in 29 CFR Part 1910

    Decompression chamber; Diving; Diving instruction; Occupational 
safety and health; Safety.

Authority and Signature

    John Henshaw, Assistant Secretary of Labor for Occupational Safety 
and Health, U.S. Department of Labor, 200 Constitution Avenue, NW., 
Washington, DC 20210, directed the preparation of this notice. 
Accordingly, the Agency issues the proposed amendment under the 
following authorities: Sections 4, 6, and 8 of the OSH Act of 1970 (29 
U.S.C. 653, 655, 657), Secretary of Labor's Order No. 5-2002 (67 FR 
65008), and 29 CFR part 1911.

    Signed at Washington, DC on January 3, 2003.
John L. Henshaw,
Assistant Secretary of Labor.

XII. Proposed Amendment to Standard

    For the reasons stated in the preamble, the Agency proposes to 
amend 29 CFR part 1910, subpart T as follows:

PART 1910--[AMENDED]

Subpart T--[AMENDED]

    1. Revise the authority citation for subpart T of part 1910 to read 
as follows:

    Authority: Sections 4, 6 and 8 of the Occupational Safety and 
Health Act of 1970 (29 U.S.C. 653, 655, and 657); sec. 107, Contract 
Work Hours and Safety Standards Act (the Construction Safety Act) 
(40 U.S.C. 333); sec. 41, Longshore and Harbor Worker's Compensation 
Act (33 U.S.C. 941); Secretary of Labor's Order Nos. 8-76 (41 FR 
25059), 9-83 (48 FR 35736), 1-90 (55 FR 9033), 6-96 (62 FR 111), 3-
2000 (65 FR 50017), or 5-2002 (67 FR 65008), as applicable; 29 CFR 
part 1911.
    2. Add new paragraph (a)(3) to Sec.  1910.401 to read as follows:


Sec.  1910.401  Scope and application.

* * * * *
    (a) * * *
    (3) Alternative requirements for recreational diving instructors 
and diving guides. Employers of recreational diving instructors and 
diving guides may forego the decompression-chamber requirements 
specified by paragraphs (b)(2) and (c)(2)(iii) of Sec.  1910.423 and 
paragraph (b)(1) of Sec.  1910.426 when they meet all of the following 
conditions:
    (i) The instructor or guide is engaging solely in recreational 
diving instruction or dive-guiding operations;
    (ii) The instructor or guide is diving within the no-decompression 
limits in these operations;
    (iii) The instructor or guide is using a nitrox breathing-gas 
mixture consisting of a high percentage of oxygen (more than 22% by 
volume) mixed with nitrogen;
    (iv) The instructor or guide is using an open-circuit, semi-closed-
circuit, or closed-circuit self-contained underwater breathing 
apparatus (SCUBA); and
    (v) The employer of the instructor or guide is complying with all 
requirements of Appendix C of this subpart.
* * * * *
    3. Add definitions for ``Dive-guiding operations'' and 
``Recreational diving instructors'' in alphabetical order to Sec.  
1910.402 to read as follows:


Sec.  1910.402  Definitions.

* * * * *
    Dive-guiding operations means leading small groups of trained 
sports divers, who use open-circuit, semi-closed-circuit, or closed-
circuit SCUBA, to local undersea diving locations for recreational 
purposes.
* * * * *
    Recreational diving instruction means training diving students in 
the use of recreational diving procedures and the safe operation of 
diving equipment, including open-circuit, semi-closed-circuit, or 
closed-circuit SCUBA during dives.
* * * * *
    4. Add a new Appendix C to 29 CFR part 1910, subpart T to read as 
follows:

Appendix C to Subpart T of Part 1910--Alternative Conditions Under 
Sec.  1910.401(a)(3) for Recreational Diving Instructors and Diving 
Guides (Mandatory)

    Paragraph (a)(3) of Sec.  1910.401 specifies that employers of 
recreational diving instructors and diving guides (hereafter, 
``divers'') who comply with all conditions in this Appendix C do not 
need to provide a decompression chamber for their recreational 
diving training and dive-guiding operations as required under Sec.  
1910.423(b)(2) or (c)(3), or Sec.  1910.426 (b)(1).

1. Equipment Requirements for Rebreathers

    (a) Employers must ensure that employees operate each rebreather 
(i.e., semi-closed-circuit and closed-circuit self-contained 
underwater breathing apparatuses (hereafter, ``SCUBAs'')) according 
to the rebreather manufacturer's instructions.
    (b) Employers are to ensure that each rebreather has a 
counterlung that supplies a volume of breathing gas to their divers 
that is sufficient to sustain the divers' respiration rate, and that 
contains a baffle system that keeps moisture from entering the 
scrubber.
    (c) Employers must place a moisture trap in the breathing loop 
of the rebreather, and ensure that:
    (i) The rebreather manufacturer approves both the moisture trap 
and its location in the breathing loop; and
    (ii) Employees use the moisture trap according to the rebreather 
manufacturer's instructions.
    (d) Employers must ensure that each rebreather has a 
continuously functioning moisture sensor, and that:
    (i) The moisture sensor connects to a visual (e.g., digital, 
graphic, analog) or auditory (e.g., voice, pure tone) alarm that is 
readily detectable by the divers under the diving conditions in 
which they operate and warns them of moisture in the breathing loop 
in sufficient time to terminate the dive and return safely to the 
surface; and
    (ii) The divers use the moisture sensor according to the 
rebreather manufacturer's instructions.
    (e) Employers are to ensure that each rebreather contains a 
continuously functioning CO2 sensor in the breathing 
loop, and that:
    (i) The rebreather manufacturer approves the location of the 
CO2 sensor in the breathing loop;
    (ii) The CO2 sensor is integrated with an alarm that 
operates in a visual (e.g., digital, graphic, analog) or auditory 
(e.g., voice, pure tone) mode that is readily detectable by the 
divers under the diving conditions in which they operate; and
    (iii) The CO2 sensor remains continuously activated 
when the inhaled CO2 level reaches and exceeds 0.005 ATA.
    (f) Before each day's diving operations, and more often when 
necessary, employers must calibrate the CO2 sensor 
according to the sensor manufacturer's instructions, and ensure 
that:
    (i) The equipment and procedures used to perform this 
calibration are accurate to within 10% of a CO2 
concentration of 0.005 ATA or less;
    (ii) They maintain this accuracy as required by the sensor 
manufacturer's instructions; and
    (iii) The calibration of the CO2 sensor is accurate 
to within 10% of a CO2 concentration of 0.005 ATA or 
less.
    (g) Employers must replace the CO2 sensor when it 
fails to meet the accuracy requirements specified above in paragraph 
1(f)(iii), and ensure that the replacement CO2 sensor 
meets the accuracy requirements specified above in paragraph 
1(f)(iii) before placing the rebreather in operation.
    (h) As an alternative to using a continuously functioning 
CO2 sensor,

[[Page 1412]]

employers may use schedules for replacing CO2-sorbent 
material provided by the rebreather manufacturer. When doing so, 
employers must use:
    (i) A CO2-sorbent replacement schedule only when the 
rebreather manufacturer has developed the replacement schedule 
according to the canister-testing protocol specified below in 
Condition 11; and
    (ii) A rebreather at a water temperature that is lower than the 
minimum, or higher than the maximum, water temperature used in the 
canister-testing protocol specified below in Condition 11 only when 
the rebreather manufacturer adds that lower or higher temperature to 
the protocol.
    (i) When using CO2-sorbent replacement schedules, 
employers must ensure that each rebreather uses a manufactured 
(i.e., commercially pre-packed), disposable scrubber cartridge 
containing a CO2-sorbent material that:
    (i) Is approved by the rebreather manufacturer;
    (ii) Removes CO2 from the diver's exhaled gas; and
    (iii) Maintains the CO2 level in the breathable gas 
(i.e., the gas that a diver inhales directly from the regulator) 
below a partial pressure of 0.01 atmospheres absolute (``ATA'').
    (j) As an alternative to manufactured, disposable scrubber 
cartridges, employers may fill CO2 scrubber cartridges 
manually with CO2-sorbent material when:
    (i) The rebreather manufacturer permits manual filling of 
scrubber cartridges;
    (ii) The employer fills the scrubber cartridges according to the 
rebreather manufacturer's instructions;
    (iii) The employer replaces the CO2-sorbent material 
using a replacement schedule developed under paragraph 1(h) above; 
and
    (iv) The employer demonstrates that manual filling meets the 
requirements specified above in paragraph 1(i).
    (k) Employers must ensure that each rebreather has an 
information module that provides:
    (i) Visual (e.g., digital, graphic, analog) or auditory (e.g., 
voice, pure tone) displays that effectively warn their divers of 
solenoid failure (when the rebreather uses solenoids) and other 
electrical weaknesses or failures (e.g., low battery voltage);
    (ii) For semi-closed circuit rebreathers, visual displays for 
the partial pressure of CO2, or deviations above and 
below a preset CO2 partial pressure of 0.005 ATA; and
    (iii) For closed-circuit rebreathers, visual displays for: 
Partial pressures of O2 and CO2, or deviations 
above and below a preset CO2 partial pressure of 0.005 
ATA and a preset O2 partial pressure of 1.40 ATA; gas 
temperature in the breathing loop; and water temperature.
    (l) Before each day's diving operations, and more often when 
necessary, employers must ensure that the electrical power supplies 
and electrical and electronic circuits in each rebreather are 
operating as required by the rebreather manufacturer's instructions.

2. Special Requirements for Closed-Circuit Rebreathers

    (a) Employers must ensure that closed-circuit rebreathers use 
supply-pressure sensors for the O2 and diluent (i.e., air 
or nitrogen) gases and continuously functioning sensors for 
detecting temperature in the inhalation side of the gas-loop and the 
ambient water.
    (b) Employers are to ensure that:
    (i) At least two O2 sensors are located in the 
inhalation side of the breathing loop; and
    (ii) The O2 sensors are: Functioning continuously; 
temperature-compensated; and approved by the rebreather 
manufacturer.
    (c) Before each day's diving operations, and more often when 
necessary, employers must calibrate O2 sensors as 
required by the sensor manufacturer's instructions. In doing so, 
they must:
    (i) Ensure that the equipment and procedures used to perform the 
calibration are accurate to within 1% of the O2 fraction 
by volume;
    (ii) Maintain this accuracy as required by the manufacturer of 
the calibration equipment;
    (iii) Ensure that the sensors are accurate to within 1% of the 
O2 fraction by volume;
    (iv) Replace O2 sensors when they fail to meet the 
accuracy requirements specified above in paragraph 2(c)(iii); and
    (v) Ensure that the replacement O2 sensors meet the 
accuracy requirements specified above in paragraph 2(c)(iii) before 
they place a rebreather in operation.
    (d) Employers must ensure that closed-circuit rebreathers have:
    (i) A gas-controller package with electrically-operated solenoid 
O2-supply valves;
    (ii) A pressure-activated regulator with a second-stage diluent-
gas addition valve;
    (iii) A manually operated gas-supply bypass valve to add 
O2 or diluent gas to the breathing loop; and
    (iv) Separate O2 and diluent-gas cylinders to supply 
the breathing-gas mixture.

3. O2 Concentration in the Breathing Gas

    Employers must ensure that the fraction of O2 in the 
nitrox breathing-gas mixture:
    (a) Is greater than the fraction of O2 in compressed 
air (i.e., exceeds 22% by volume);
    (b) For open-circuit SCUBA, never exceeds a maximum fraction of 
breathable O2 of 40% by volume or a maximum O partial 
pressure of 1.40 ATA, whichever exposes divers to less 
O2; and
    (c) For rebreathers, never exceeds a maximum O2 
partial pressure of 1.40 ATA.

4. Limiting O2 Partial Pressure and Diving Depth

    (a) Regarding O2 exposure, employers must:
    (i) Ensure that the exposure of their divers to partial 
pressures of O2 between 0.60 and 1.40 ATA does not exceed 
the 24-hour single-exposure time limits specified either by the 2001 
National Oceanic and Atmospheric Administration Diving Manual (the 
``2001 NOAA Diving Manual'') or by the report entitled ``Enriched 
Air Operations and Resources Guide,'' published in 1995 by the 
Professional Association of Diving Instructors (known commonly as 
the ``1995 DSAT Oxygen Exposure Table'') (see References (1) and (2) 
at the end of this appendix for complete information regarding these 
references); and
    (ii) Determine a diver's O2-exposure duration using 
the diver's maximum O2 exposure (partial pressure of 
O2) during the dive and the total dive time (i.e., from 
the time the diver leaves the surface until the diver returns to the 
surface).
    (b) Regardless of the diving equipment used, employers must 
ensure that their divers do not exceed a depth of 130 feet of sea 
water (``fsw'') or to a maximum O2 partial pressure of 
1.40 ATA, whichever exposes them to less O2.

5. Mixing and Analyzing the Breathing Gas

    (a) Employers must ensure that:
    (i) Properly trained personnel mix nitrox-breathing gases, and 
that nitrogen is the only inert gas used in the breathing-gas 
mixture; and
    (ii) When mixing nitrox-breathing gases, they mix the 
appropriate breathing gas before delivering the mixture to the 
breathing-gas cylinders, using the continuous-flow or partial-
pressure mixing techniques specified in the 2001 NOAA Diving Manual, 
or using a filter-membrane system.
    (b) Before the start of each day's diving operations, employers 
must determine the O2 fraction of the breathing-gas 
mixture using an O2 analyzer. In doing so, they must:
    (i) Ensure that the O2 analyzer is accurate to within 
1% of the O2 fraction by volume; and
    (ii) Maintain this accuracy as required by the manufacturer of 
the analyzer.
    (c) When the breathing gas is a commercially supplied nitrox 
breathing-gas mixture, employers must ensure that the O2 
is Grade A (also known as ``aviator's oxygen'') or Grade B (referred 
to as ``industrial-medical oxygen''), and meets the specifications, 
including the purity requirements, found in the ANSI-Compressed Gas 
Association Commodity Specification for Air, G-7.1-1997. In 
addition, employers are to ensure that the commercial suppliers:
    (i) Determine the O2 fraction in the breathing-gas 
mixture using an analytic method that is accurate to within 1% of 
the O2 fraction by volume;
    (ii) Make this determination when the mixture is in the charged 
tank and after disconnecting the charged tank from the charging 
apparatus;
    (iii) Document the O2 fraction in the mixture; and
    (iv) Provide the employer with a written certification of the 
O2 analysis.
    (d) Before producing nitrox breathing-gas mixtures using a 
compressor in which the gas pressure in any system component exceeds 
125 pounds per square inch (psi), employers must:
    (i) Have the compressor manufacturer certify in writing that the 
compressor is suitable for mixing high-pressure air with the highest 
O2 fraction used in the nitrox breathing-gas mixture;
    (ii) Ensure that the compressor is oil-less or oil-free and 
rated for O2 service, unless they comply with the 
requirements of paragraph 5(e) below; and
    (iii) Ensure that the compressor meets the requirements 
specified in paragraphs (i)(1) and (i)(2) of Sec.  1910.430 whenever 
the highest O2 fraction used in the mixing process 
exceeds 40%.

[[Page 1413]]

    (e) Before employers produce nitrox breathing-gas mixtures using 
an oil-lubricated compressor to mix high-pressure air with 
O2, and regardless of the gas pressure in any system 
component, they must:
    (i) Use only uncontaminated air (i.e., air containing no 
hydrocarbon particulates) for the nitrox breathing-gas mixture;
    (ii) Have the compressor manufacturer certify in writing that 
the compressor is suitable for mixing the high-pressure air with the 
highest O2 fraction used in the nitrox breathing-gas 
mixture;
    (iii) Filter the high-pressure air to produce O2-
compatible air;
    (iv) Have the filter-system manufacturer certify in writing that 
the filter system used for this purpose is suitable for producing 
O2-compatible air; and
    (v) Continuously monitor the air downstream from the filter for 
hydrocarbon contamination.
    (f) Employers are to ensure that diving equipment using nitrox 
breathing-gas mixtures or pure O2 under high pressure 
(i.e., exceeding 125 psi) conforms to the O2-service 
requirements specified in paragraphs (i)(1) and (i)(2) of Sec.  
1910.430.

6. Use of No-Decompression Limits

    (a) For diving conducted while using nitrox breathing-gas 
mixtures, employers must ensure that each of their divers remains 
within the no-decompression limits specified for single and 
repetitive air diving and published in the 2001 NOAA Diving Manual 
or the report entitled ``Development and Validation of No-Stop 
Decompression Procedures for Recreational Diving: The DSAT 
Recreational Dive Planner,'' published in 1994 by Hamilton Research 
Ltd. (known commonly as the ``1994 DSAT No-Decompression Tables''). 
(See References (1) and (3) at the end of this appendix for complete 
information regarding these references.)
    (b) Employers may permit their divers to use dive-decompression 
computers designed to regulate decompression when the dive-
decompression computer uses the no-decompression limits specified 
above in paragraph 6(a), and provides output that reliably 
represents those limits.

7. Emergency Egress

    (a) Regardless of the diving equipment used by divers (i.e., 
open-circuit SCUBA or rebreathers), employers must ensure that the 
diving equipment consists of an open-circuit emergency-egress system 
(a ``bail-out'' system) in which the second stage of the regulator 
connects to a separate supply of emergency breathing gas, and the 
emergency breathing gas consists of air or the same nitrox 
breathing-gas mixture used during the dive.
    (b) For open-circuit SCUBA, employers may use as an alternative 
to the ``bail-out'' system specified above under Condition (7)(a), 
the emergency-egress system (i.e., the reserve breathing-gas supply) 
specified for open-circuit SCUBA by Sec.  1910.424(c)(4)(i).
    (c) Employers must ensure that the bail-out or alternative 
system performs reliably and provides sufficient emergency breathing 
gas to enable the diver to terminate the dive and return safely to 
the surface.

8. Treating Diving-Related Medical Emergencies

    (a) Before each day's diving operations, employers must:
    (i) Verify that a hospital, qualified health-care professionals, 
and the nearest Coast Guard Coordination Center (or an equivalent 
rescue service operated by a State, county, or municipal agency) are 
available to treat diving-related medical emergencies;
    (ii) Ensure that each dive site has a means to alert these 
treatment resources in a timely manner when a diving-related medical 
emergency occurs; and
    (iii) Ensure that transportation to a suitable decompression 
chamber is readily available when no decompression chamber is at the 
dive site, and that this transportation can deliver the injured 
diver to the decompression chamber within two (2) hours travel time 
from the dive site.
    (b) Employers must ensure that portable O2 equipment 
is available at the dive site to treat injured divers. In doing so, 
employers must ensure that:
    (i) The equipment delivers medical-grade O2 that 
meets the requirements for Medical USP oxygen (Type I, Quality 
Verification Level A) of CGA G-4.3-2000 (``Commodity Specification 
for Oxygen'');
    (ii) The equipment delivers this O2 to a transparent 
mask that covers the injured diver's nose and mouth; and
    (iii) Sufficient O2 is available for administration 
to the injured diver from the time the employer recognizes the 
symptoms of a diving-related medical emergency until the injured 
diver reaches a decompression chamber for treatment.
    (c) Before each day's diving operations, employers must:
    (i) Ensure that at least two attendants, either employees or 
non-employees, qualified in first-aid and administering 
O2 treatment are available at the dive site to treat 
diving-related medical emergencies; and
    (ii) Verify their qualifications for this task.

9. Diving Logs and Decompression Tables

    (a) Before starting each day's diving operations, employers 
must:
    (i) Designate an employee or a non-employee to make entries in a 
diving log; and
    (ii) Verify that this designee understands the diving and 
medical terminology, and proper procedures, for making correct 
entries in the diving log.
    (b) Employers are to:
    (i) Ensure that the diving log conforms to the requirements 
specified by paragraph (d) (``Record of dive'') of Sec.  1910.423; 
and
    (ii) Keep a record of the dive in accordance with Sec.  1910.440 
(``Recordkeeping requirements'').
    (c) Employers must ensure that a hard-copy of the decompression 
tables used for the dives (as specified above in paragraph 6(a)) is 
readily available at the dive site, whether or not your divers use 
dive-decompression computers.

10. Diver Training

    Employers must ensure that their divers receive training that 
enables them to perform their work safely and effectively while 
using open-circuit SCUBAs or rebreathers supplied with nitrox 
breathing-gas mixtures. Accordingly, the divers must be able to 
demonstrate that they can perform critical tasks safely and 
effectively, including, but not limited to: Recognizing the effects 
of breathing excessive CO2 and O2; taking 
appropriate action after detecting excessive levels of 
CO2 and O2; and properly evaluating, 
operating, and maintaining their diving equipment under the diving 
conditions they encounter.

11. Testing Protocol for Determining the CO2 Limits of 
Rebreather Canisters

    (a) Employers must ensure that the rebreather manufacturer used 
the following procedures for determining that the CO2-
sorbent material meets the specifications of the material's 
manufacturer:
    (i) The NATO CO2 absorbent-activity test;
    (ii) The RoTap shaker and nested sieves;
    (iii) The Navy Experimental Diving Unit (``NEDU'')-derived 
Schlegel test; and
    (iv) The NEDU's MeshFit software;
    (b) Employers must ensure that the rebreather manufacturer 
applied the following canister-testing materials, methods, 
procedures, and statistical analyses:
    (i) A nitrox breathing-gas mixture that has an O2 
fraction maintained at 0.28 (equivalent to 1.4 ATA of O2 
at 130 fsw, the maximum O2 concentration permitted at 
this depth);
    (ii) While operating the rebreather at a maximum depth of 130 
fsw, used a breathing machine to continuously ventilate the 
rebreather with breathing gas that is at 100% humidity and warmed to 
a temperature of 98.6 degrees F (37 degrees C) in the heating-
humidification chamber;
    (iii) Measured the O2 concentration of the inhalation 
breathing gas delivered to the mouthpiece;
    (iv) Tested the canisters using the three ventilation rates 
listed in the following table (with the required breathing-machine 
tidal volumes and frequencies, and CO2-injection rates, 
provided for each ventilation rate):

------------------------------------------------------------------------
                                      Breathing machine
 Ventilation rates      Breathing        frequencies      CO2 injection
  (Lpm, ATPS \1\)     machine tidal      (breaths per      rates (Lpm,
                       volumes (L)          min.)           STPD \2\)
------------------------------------------------------------------------
        22.5                1.5                 15              0.90
        40.0                2.0                 20              1.35
        62.5                2.5                 25             2.25
------------------------------------------------------------------------
\1\ ATPS means ambient temperature and pressure, saturated with water.
\2\ STPD means standard temperature and pressure, dry; the standard
  temperature is 32 degrees F (0 degrees C).

    (v) When using a work rate (i.e., breathing-machine tidal volume 
and frequency) other than the work rates listed in the table above, 
added the appropriate combinations of ventilation rates and 
CO2-injection rates;
    (vi) Performed the CO2 injection at a constant 
(steady) and continuous rate during each testing trial;
    (vii) Determined canister duration using a minimum of four (4) 
water temperatures, including 40, 50, 70, and 90 degrees F (4.4, 
10.0, 21.1, and 32.2 degrees C, respectively).
    (viii) Monitored the breathing-gas temperature at the rebreather 
mouthpiece (at

[[Page 1414]]

the ``chrome T'' connector), and ensured that this temperature 
conforms to the temperature of a diver's exhaled breath at the water 
temperature and ventilation rate used during the testing trial; \9\
---------------------------------------------------------------------------

    \9\ NEDU can provide the manufacturer with information on the 
temperature of a diver's exhaled breath at various water 
temperatures and ventilation rates, as well as techniques and 
procedures used to maintain these temperatures during the testing 
trials.
---------------------------------------------------------------------------

    (ix) Implemented at least eight (8) testing trials for each 
combination of temperature and ventilation-CO2-injection 
rates (e.g., eight testing trials at 40 degrees F using a 
ventilation rate of 22.5 Lpm at a CO2-injection rate of 
0.90 Lpm);
    (x) Allowed the water temperature to vary no more than +/- 2.0 
degrees F (+/- 1.0 degree C) between each of the eight testing 
trials, and no more than +/- 1.0 degree F (+/- 0.5 degree C) within 
each testing trial;
    (xi) Used the average temperature for each set of eight testing 
trials in the statistical analysis of the testing-trial results, 
with the testing-trial results being the time taken for the inhaled 
breathing gas to reach 0.005 ATA of CO2 (i.e., the 
canister-duration results);
    (xii) Analyzed the canister-duration results using the repeated-
measures statistics described in NEDU Report 2-99 (see Reference (4) 
at the end of this appendix for complete information regarding this 
reference);
    (xiii) Specified the replacement schedule for the 
CO2-sorbent materials in terms of the lower prediction 
line (or limit) of the 95% confidence interval; and
    (xiv) Derived replacement schedules only by interpolating among, 
but not by extrapolating beyond, the depth, water temperatures, and 
exercise levels used during canister testing.

12. References

    This section provides detailed information regarding the 
references cited in this appendix.
    (1) National Oceanic and Atmospheric Administration (2001). NOAA 
Diving Manual: Diving for Science and Technology. Joiner, J. T. 
(ed.). Best Publishing Co., Flagstaff, AZ.
    (2) Diving Science and Technology (1995). ``Analysis of Proposed 
Oxygen Exposure Limits for DSAT Oxygen Exposure Table Against 
Existing Database of Manned Oxygen Test Dives.'' Enriched Air 
Operations and Resource Guide. International PADI, Inc., Rancho 
Santa Margarita, California.
    (3) R. W. Hamilton, R. E. Rogers, M. R. Powell, and R. D. Vann 
(1994). ``Development and Validation of No-Stop Decompression 
Procedures for Recreational Diving: The DSAT Recreational Dive 
Planner.'' Hamilton Research, Ltd., Tarrytown, New York.
    (4) J. R. Clarke. ``Statistically Based CO2 Canister 
Duration Limits for Closed-Circuit Underwater Breathing Apparatus.'' 
U.S. Navy Experimental Diving Unit, Report 2-99, 1999.
* * * * *
[FR Doc. 03-372 Filed 1-9-03; 8:45 am]
BILLING CODE 4510-26-P