[Federal Register Volume 69, Number 31 (Tuesday, February 17, 2004)]
[Rules and Regulations]
[Pages 7351-7366]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-3289]


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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: Final rule.

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SUMMARY: OSHA is issuing this final rule to amend its Commercial Diving 
Operations (CDO) standards. This final rule allows employers of 
recreational diving instructors and diving guides to comply with an 
alternative set of requirements instead of the decompression-chamber 
requirements in the current CDO standards. The final rule applies only 
when these employees engage in recreational diving instruction and 
diving-guide duties; use an open-circuit, a semi-closed-circuit, or a 
closed-circuit self-contained underwater-breathing apparatus supplied 
with a breathing gas that has a high percentage of oxygen mixed with 
nitrogen; dive to a maximum depth of 130 feet of sea water; and remain 
within the no-decompression limits specified for the partial pressure 
of nitrogen in the breathing-gas mixture. These alternate requirements 
essentially are the same as the terms of a variance granted by OSHA to 
Dixie Divers, Inc. in 1999.

DATES: This final rule becomes effective on March 18, 2004.

ADDRESSES: In compliance with 28 U.S.C. 2112(a), OSHA designates the 
Associate Solicitor of Labor for Occupational Safety and Health as the 
recipient of petitions for review of this final rule. Submit petitions 
of review to the Associate Solicitor at: Office of the Solicitor of 
Labor, Room S-4004, U.S. Department of Labor, 200 Constitution Avenue, 
NW., Washington, DC 20210.

FOR FURTHER INFORMATION CONTACT: For general information and press 
inquiries, contact Mr. George Shaw, Office of Communications, Room N-
3647, OSHA, U.S. Department of Labor, 200 Constitution Avenue, NW., 
Washington, DC 20210; telephone (202) 693-1999. For technical 
inquiries, contact Mr. Robert Bell, Directorate of Standards and 
Guidance, Room N-3609, OSHA, U.S. Department of Labor, 200 Constitution 
Avenue, NW., Washington, DC 20210; telephone (202) 693-2053 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 ``2003.''

SUPPLEMENTARY INFORMATION:

Table of Contents

    The following Table of Contents identifies the major sections under 
Supplementary Information, including a detailed summary and explanation 
of the final rule.

I. Background
II. Summary and Explanation of the Rule
    A. Final Sec.Sec. 1910.401(a)(3) and 1910.402 (``Definitions'')
    B. Conditions Specified in Final Appendix C
III. Legal Considerations
IV. Final Economic Analysis and Regulatory Flexibility Certification
V. Paperwork Reduction Act
VI. Federalism
VII. State Plans
VIII. Unfunded Mandates
IX. Applicability of Existing Consensus Standards
    List of Subjects in 29 CFR Part 1910
X. Authority and Signature

I. Background

    In 1999, acting under section 6(d) of the Occupational Safety and 
Health Act of 1970 (``OSH Act'' 29 U.S.C. 655), the Occupational Safety 
and Health Administration (``OSHA'' or ``the Agency'') published an 
order granting a permanent variance to Dixie Divers, Inc. (``Dixie 
Divers'') (Ex. 2-11). The permanent variance exempted Dixie Divers 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 (hereafter, 
``divers'') engage in underwater instructional and guiding operations.
    The purpose of having a decompression chamber available and

[[Page 7352]]

ready for use at a dive site is to treat decompression sickness (DCS) 
and arterial gas embolism (AGE). DCS may occur from breathing air or 
mixed gases at diving depths and durations that require decompression, 
while AGE may result from over-pressurizing the lungs, usually 
following a rapid ascent to the surface during a dive without proper 
exhalation.
    The Dixie Diver variance from the decompression-chamber 
requirements applied only to mixed-gas diving operations at a maximum 
depth of 130 feet of sea water (``fsw'') performed within no-
decompression limits. During these diving operations, divers use 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 self-contained 
underwater breathing apparatus (SCUBA). In issuing the permanent 
variance, the Agency noted that compliance would provide divers with a 
level of protection that met or exceeded the level of protection they 
would receive if they had access to a decompression chamber at the dive 
site as required by Sec.Sec. 1910.423(b)(2) and (c)(3)(iii), and 
1910.426(b)(1).
    On January 10, 2003, OSHA proposed to amend its Commercial Diving 
Operations (``CDO'') standards to incorporate the terms and conditions 
of the Dixie Divers variance as an appendix to the CDO standards (68 FR 
1399). The Agency now is issuing the final rule to amend the CDO 
standards based on this proposal. OSHA believes that this amendment 
enables recreational diving instructors and diving guides to extend 
their diving operations while minimizing their risk of DCS and AGE. The 
Agency concludes that the recreational diving instructors and diving 
guides covered by this amendment will receive a level of safety and 
health protection that is equivalent to recreational diving instructors 
and diving guides who have a decompression chamber located at the dive 
site during mixed-gas diving operations regulated under the CDO 
standards. Therefore, a decompression chamber near the dive site is 
unnecessary for the divers covered by this final rule.

II. Summary and Explanation of the Final Rule

    OSHA received no requests for a hearing on the proposed amendment, 
thereby enabling it to proceed directly to this final rule after 
considering the comments submitted by the public in response to the 
proposal. In this regard, the Agency received 13 public comments on the 
proposal. However, two commenters each submitted a duplicate set of 
responses (Exs. 6-6 and 6-7, and 6-8 and 6-9); one set of duplicate 
responses (Exs. 6-6 and 6-7) was received from a commercial diver that 
involved an issue unrelated to this rulemaking. We address the 
remaining comments in sections A and B below, which discuss the 
conditions adopted in the final rule.
    When the discussion regarding a condition does not cite a comment, 
then the public did not comment on that condition. In such cases, we 
have assumed that the regulated community found the proposed condition 
to be appropriate and necessary for diver safety based on OSHA's stated 
rationale in the proposed rule, and we have retained it in the final 
rule without further explanation (see 68 FR 1399, pages 1400-1409).

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

    Proposed Sec. 1910.401(a)(3) specified that this amendment would 
apply only to recreational diving instructors and diving guides who are 
engaged solely in recreational diving instruction and dive-guiding 
operations. Accordingly, OSHA also proposed to add the following 
definitions for ``recreational diving instruction'' and ``dive-guiding 
operations'' to Sec. 1910.402 of the CDO standards:

    ``Recreational diving instruction'' means 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.
    ``Dive-guiding operations'' means 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.

    To further limit application of the amendment, proposed Sec. 
1910.401(a)(3) required employers to ensure that the instructors and 
guides conduct these dives within the no-decompression limits, and that 
they 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 
SCUBA. Under this proposed requirement, employers also would have to 
comply with the requirements specified in new Appendix C of subpart T.
    Based on its analysis of the record, OSHA is adopting proposed 
Sec.Sec. 1910.401(a)(3) and 1910.402 in the final rule. Recreational 
diving instructors and diving guides who use a nitrox breathing-gas 
mixture supplied by an open-circuit, semi-closed-circuit, or closed-
circuit SCUBA under no-decompression diving limits will receive a level 
of safety and health protection equivalent to the recreational diving 
instructors and diving guides who have a decompression chamber located 
at the dive site during mixed-gas diving operations regulated under the 
CDO standards.

B. Conditions Specified in Final Appendix C

    OSHA proposed to add a new appendix to the CDO standards to specify 
the conditions under which employers may use this alternative to 
decompression chambers. Accordingly, the Agency is adopting new 
Appendix C in the final rule after revising the proposal based on 
comments submitted to the record. The following discussion addresses 
the comments received on the proposed conditions, and what OSHA is 
including in the final rule.
1. Equipment Requirements for Rebreathers
    (a) Manufacturer's instructions. As proposed, this condition 
required employers to ensure that their recreational diving instructors 
and diving guides use rebreathers (i.e., semi-closed circuit and 
closed-circuit SCUBA) according to the rebreather manufacturer's 
instructions. OSHA is retaining this condition in the final rule. As 
noted in the proposal, the Agency believes that SCUBA manufacturers are 
best qualified to identify and specify the components, configuration, 
and operation of their products.
    (b) Counterlungs. This proposed condition required employers to 
ensure that each rebreather has a counterlung (also referred to as an 
``inhalation bag'' or ``breathing bag'') that both contains a baffle 
system that prevents moisture from entering the scrubber or breathing 
hoses and supplies a sufficient volume of breathing gas to the divers 
to sustain their respiration rate during diving operations. The 
National Oceanic and Atmospheric Administration (NOAA) considers 
counterlungs a necessity for rebreather diving (see Ex. 3-12, p. 14-3). 
OSHA expects rebreather manufacturers to provide the purchaser or user 
with information regarding this displacement as part of their usual and 
customary practice. In addition, by keeping moisture from entering the 
scrubber, baffle systems prevent rapid deterioration of the 
CO2-sorbent material housed in the scrubber and decrease the 
risk of CO2 toxicity (see Ex. 3-12, p. 14-8).
    The Agency received one comment (Ex. 5-2-1) regarding the proposed

[[Page 7353]]

baffle-system requirement. This commenter recommended revising the 
condition to read that the counterlung must contain ``a baffle system 
and/or other moisture separating system that keeps moisture from 
entering the scrubber.'' In justifying this revision, the commenter 
stated: ``While all manufactured units have some sort of system to 
accomplish this function, all do not call it a ``baffle'' system. 
Additionally, use of the specific term may * * * create problems for 
future technological developments, which may address the problem in 
different ways.'' OSHA agrees with this commenter that the proposed 
wording was too specific, and might hinder future efforts to develop 
new technologies to prevent moisture from entering the scrubber. 
Therefore, the final rule adopts the language of the proposed condition 
except for the part addressing baffle systems; for this part, the 
Agency is adopting the language recommended by this commenter.
    (c) Moisture traps. Under this proposed condition, employers need 
to place a moisture trap in the breathing loop of each rebreather. The 
employer also must ensure that the rebreather manufacturer approves 
both the moisture trap and its location in the breathing loop, and that 
their divers use the moisture trap according to the rebreather 
manufacturer's instructions. The Agency is retaining this condition in 
the final rule as proposed because it believes that moisture traps, 
when approved by the rebreather manufacturer and located and used 
according to the manufacturer's instructions, prevent water from 
entering the CO2-absorbing canisters. By preventing such 
water leakage, moisture traps preserve the CO2-absorbing 
properties of the sorbent material inside the canister.
    (d) Moisture sensors. Under this proposed condition, 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. This alarm must be readily 
detectable by divers under the diving conditions in which they operate 
and warn them of moisture in the breathing loop in sufficient time for 
them to terminate the dive and return safely to the surface. 
Additionally, the proposed condition required employers to ensure that 
their divers use the moisture sensors according to the rebreather 
manufacturer's instructions. By warning divers of hazardous water 
leakage into the canister, moisture sensors allow divers to return to 
the surface before CO2 in the recycled breathing gas reaches 
dangerous levels. Therefore, the final rule includes these requirements 
as proposed.
    (e) CO2 sensors. An important component in controlling excessive 
CO2 is the CO2 sensor. In the proposal, this 
condition required employers to ensure that each rebreather contains a 
continuously functioning CO2 sensor in the breathing loop. 
It also specified that the rebreather manufacturer must approve the 
CO2 sensor and its location in the breathing loop. In 
addition, employers must ensure that the CO2 sensor is 
integrated with an alarm that operates in a visual (e.g., digital, 
graphic, or analog) or auditory (e.g., voice, pure tone) mode readily 
detectable by divers under the diving conditions in which they operate. 
This alarm would remain continuously activated when the inhaled 
CO2 level reaches and exceeds 0.005 atmospheres absolute 
(``ATA'').\1\ In the final rule, OSHA is retaining the condition as 
proposed.
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    \1\ ATA 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. This proposed condition stated 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. Additionally, employers must 
maintain the accuracy of the equipment and procedures used to perform 
the calibration to within 10% of a CO2 concentration of 
0.005 ATA or less according to the sensor manufacturer's instructions. 
Using this equipment, they would calibrate the CO2 sensor to 
within 10% of a CO2 concentration of 0.005 ATA or less. The 
Agency is including this condition in the final rule because it 
concludes that this calibration requirement is necessary to identify 
improperly functioning CO2 sensors.
    (g) Faulty CO2 sensors.In the proposal, this condition specified 
that employers must replace CO2 sensors that fail the 
accuracy requirements delineated above in Condition 1(f)(iii) with a 
sensor that meets these requirements. Eliminating sensors that are 
unreliable or that cannot function under rugged diving conditions is 
necessary to provide divers with safe breathing gas. OSHA is retaining 
this requirement in the final rule.
    (h) CO2-sorbent materials. As an alternative to using continuously 
functioning CO2 sensors, the proposed condition allowed an 
employer to implement a rebreather manufacturer's schedule for 
replacing the CO2-sorbent material in the canister of a 
rebreather. However, the manufacturer would have to develop the 
schedule according to the canister-testing protocol specified in 
Condition 11 of Appendix C (``Testing Protocol for Determining the 
CO2 Limits of Rebreather Canisters''). Additionally, the 
employer may use the rebreather at a water temperature that is lower 
than the minimum, or higher than the maximum, water temperature used in 
the testing protocol specified in Condition 11, but only when the 
rebreather manufacturer adds that lower or higher temperature to the 
testing protocol.
    A commenter (Ex. 5-2-1) stated that the proposed language regarding 
the minimum and maximum water-temperature requirement was confusing, 
and recommended that the requirement read as follows: ``A rebreather 
within the temperature range for which the manufacturer conducted its 
scrubber canister tests following the protocol specified in Condition 
11. Variations above or below the range are acceptable only after the 
manufacturer adds that lower or higher temperature to the protocol.'' 
OSHA agrees that the commenter's revision expresses more clearly than 
the proposal the meaning of this provision, and has revised this 
language in the final rule accordingly. The Agency believes that the 
canister-replacement schedule provides a reliable estimate of canister 
duration that incorporates an assessment of the physical properties of 
the CO2-sorbent material and an evaluation of the canister's 
effectiveness.
    (i) Commercially pre-packed cartridges. This proposed condition 
required employers who use a CO2-sorbent replacement 
schedule specified in Condition 1(h) to ensure that each rebreather 
uses a manufactured (i.e., commercially pre-packed), disposable 
scrubber cartridge. This cartridge would have to 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 would 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.
    OSHA is including this condition in the final rule as proposed. 
These requirements ensure proper compression and uniform distribution 
of the sorbent material in the cartridge, thereby minimizing 
``channeling'' in the

[[Page 7354]]

material \2\ and lowering the diver's risk of rebreathing exhaled 
breathing gas that is high in CO2.
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    \2\ ``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. Channeling 
can be prevented by compressing 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. This 
proposed condition permitted employers to fill CO2 scrubber 
cartridges manually instead of using commercially pre-packed 
cartridges. This practice is acceptable when the rebreather 
manufacturer designs the scrubber cartridge to be filled manually, 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 Conditions 1(h) and 1(i). OSHA is 
adopting this condition in the final rule as proposed because manually 
filled cartridges that meet the performance requirements for 
commercially pre-packed cartridges will remove CO2 
effectively from the breathing loop.
    (k) Information module. In the proposal, this condition required 
employers to ensure that their divers use an information module that 
provides them with critical information regarding rebreather operation. 
For all rebreathers, the module needed to 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 needed to 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 would 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. The module also needed to have a visual display 
for both gas temperature in the breathing loop and water temperature.
    OSHA is including these requirements in the final rule as proposed 
because warning divers of electrical weaknesses and failures informs 
them not to rely on their electrically operated equipment and to take 
protective actions. Providing information about O2 and 
CO2 partial pressures alerts divers to rising and 
potentially toxic levels of these gases in time for them to prevent 
extended exposure. Additionally, information regarding water 
temperature warns divers of the risk of hypothermia, while gas-
temperature information allows divers to estimate the duration of their 
CO2-sorbent material.
    (l) Checking electrical power and circuits. Under this proposed 
condition, employers would ensure that the electrical power supplies 
and electrical and electronic circuits in each rebreather are operating 
according to the rebreather manufacturer's instructions. Employers must 
check for proper operation prior to beginning diving operations each 
day, and more often when necessary. The Agency is adopting this 
condition as proposed because partial or total electronic failures 
could interfere with rebreather sensor and control systems.
2. Special Requirements for Closed-Circuit Rebreathers
    (a) Supply-pressure and temperature sensors. This proposed 
condition stated that employers are responsible for ensuring 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. OSHA is 
including it in the final rule as proposed. In this regard, supply-
pressure sensors inform divers of the remaining supply of breathing-gas 
ingredients (i.e., O2 and air or nitrogen), thereby enabling 
them to monitor their breathing-gas consumption during a dive. Low gas 
supplies alert divers to an unusually high consumption of breathing 
gas, indicating a possible problem with the rebreather. An unexpected 
gas loss also may 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. In addition, OSHA 
believes that temperature sensors increase diver safety because the 
sensors alert divers to the possibility of hypothermia. Temperature 
reductions in breathing gas also inform divers that the efficiency of 
the CO2-sorbent material is likely to deteriorate (Ex. 3-
11).
    (b) O2 sensors. As proposed, this condition required 
employers to ensure that at least two O2 sensors are located 
in the inhalation side of the breathing loop. These O2 
sensors must function continuously, compensate for variations in 
temperature, and be approved by the rebreather manufacturer. The Agency 
is including the condition in the final rule as proposed because the 
sensors provide divers with critical information regarding 
O2 levels in the breathing gas. Accurate information about 
O2 levels enables divers to maintain appropriate amounts of 
O2 in the breathing gas, thereby minimizing the need for 
emergency escape.
    (c) Calibrating O2 sensors. This proposed condition 
specified that employers must calibrate O2 sensors as 
required by the sensor manufacturer's instructions before the start of 
each day's diving operations and more often when necessary. In 
performing this requirement, employers would: (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 specified accuracy requirements; and 
(v) ensure that the replacement O2 sensors meet these 
accuracy requirements.
    OSHA believes that the levels of accuracy specified under this 
condition provide an adequate safety margin for the divers to detect 
anomalous O2 concentrations, to identify the cause of the 
anomaly and adjust breathing-system controls accordingly, and to ascend 
to the surface when necessary. Additionally, proper and timely 
calibration of O2 sensors, as well as accurate information 
regarding the level of O2 in the breathing loop, provides 
divers with an opportunity to take corrective action should the 
O2 level exceed the specified parameters. Maintaining proper 
O2 levels will prevent the central nervous system and 
pulmonary effects of O2 toxicity, and will protect divers 
from death and injury. Accordingly, the Agency is including these 
O2-sensor requirements in the final rule as proposed.
    (d) Controlling O2 delivery. This proposed condition 
stated that employers are to ensure that closed-circuit rebreathers 
have: (i) A gas-controller package with solenoid O2-supply 
valves that are operated electronically; (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. Accordingly, 
closed-circuit rebreathers would automatically inject

[[Page 7355]]

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 also 
must be able to control these functions manually using gas-supply 
bypass valves provided on the equipment. Separate cylinders would 
provide the O2 and diluent gas used in the breathing-gas 
mixture.
    OSHA is adopting the condition as proposed because these equipment 
requirements maintain O2 levels in the breathing gas within 
a specified range of partial pressures. This condition provides 
assurance that a sufficient and reliable breathing-gas pressure is 
available to deliver breathable gas to the diver without adversely 
affecting breathing effort. Maintaining a comfortable breathing effort 
reduces CO2 accumulation caused by an increased rate of 
breathing and, in turn, lowers the risk of CO2 toxicity. 
Additionally, by maintaining O2 in the breathing loop at 
specified levels, the condition ensures that divers remain within pre-
established O2 exposure limits. Finally, the condition 
allows divers to manually add O2 or diluent gas from 
separate cylinders, enabling them to adjust the components of the 
breathing-gas mixture should the gas-controller package and pressure-
activated regulator fail.
3. O2 Concentration in the Breathing Gas
    Under this proposed condition, employers would be responsible for 
ensuring that the fraction of O2 in the nitrox breathing-gas 
mixture exceeds 22% by volume.\3\ For rebreathers, the fraction of 
O2 would never exceed an O2 partial pressure of 
1.40 ATA, while for open-circuit SCUBA, the O2 fraction 
would never exceed 40% by volume or an O2 partial pressure 
of 1.40 ATA, whichever exposed divers to less O2.
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    \3\ Although low O2 levels are rare under nitrox 
breathing conditions, the sensors also would detect levels of 
O2 less than 22% by volume (see Condition 3 of Appendix C 
below).
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    One commenter (Ex. 6-2) responded to this proposed condition by 
stating, ``The concept that diving with a higher concentration of 
[O2] than compressed air removes the risk of DCS is 
ludicrous. Any level of nitrogen predisposes individuals to the 
likelihood of DCS. * * * '' The following comment submitted by Dr. 
Larry Raymond (Ex. 5-1), an occupational-health physician with 
experience in treating diving-related injuries, addressed this issue:

    Oxygen-rich mixtures of nitrogen and oxygen (``Nitrox'') have 
indeed been shown to be advantageous[] with regard to decompression 
sickness (DCS). Nitrox allows longer dives at a given depth (vs. air 
dives). Nitrox is [] safe, as long as meticulous care is given to 
gas mixing, lubrication of oxygen-exposed surfaces (avoid fire), and 
compliance with depth limits and decompression schedules.

    Although the Agency believes that increased O2 levels 
can reduce the risk of DCS by displacing nitrogen in the nitrox 
breathing-gas mixture, it notes that the major purpose of this 
condition is to prevent O2 toxicity or hypoxia, not to 
remove the risk of DCS. Another commenter (Ex. 6-1), who had three 
years of experience with nitrox breathing-gas mixtures as a recovery 
diver and diving instructor, recommended that ``any diver who is 
engaged in recreational diving with open-circuit [SCUBA], be supplied 
with a breathing gas consisting of a high percentage of oxygen mixed 
with nitrogen.'' This recommendation attests to the health and safety 
benefits of nitrox breathing-gas mixtures, as incorporated in the final 
rule.
    OSHA is including this condition in the final rule as proposed 
because it finds that the minimal level of 22% is consistent with the 
minimal level required for nitrox breathing-gas mixtures.\4\ 
Additionally, the Agency is including in the final rule the upper 
limits designated for the O2 component in the nitrox 
breathing-gas mixture as proposed (i.e., 40% by volume and 1.40 ATA). 
The 40% limit specifies the level above which equipment exposed to 
O2 (e.g., SCUBA cylinders, valves, first-stage regulators, 
high-pressure hoses) must be rated for O2 service because of 
the increased risk of an O2-accelerated explosion (Ex. 3-12, 
p. 15-18), while the 1.40-ATA limit represents the maximum level of 
O2 exposure that effectively will prevent O2 
toxicity among divers (see Ex. 3-4, pp. 3-5 through 3-15 and P-37 
through P-45, and Ex. 3-10).
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    \4\ By definition, a nitrox breathing-gas mixture must contain a 
higher percentage of oxygen than is found in normal air (i.e., 21%), 
usually 32% and 36% oxygen (Ex. 3-12).
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4. Regulating O2 Exposures and Diving Depth
    (a) Limiting O2 partial pressure. This proposed condition 
identified procedures for preventing O2 toxicity. Employers 
would have to: (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 (Ex. 3-12, p. 3-23) or by the 1995 Diving Science 
and Technology Corporation (DSAT) report contained in the publication 
entitled ``Enriched Air Operations and Resource Guide'' (Ex. 3-13, p. 
34).
    Under this condition, paragraph (i) reduces the risk of developing 
O2 toxicity by regulating O2 exposures according 
to increases in O2 partial pressure (i.e., dive depth) and 
dive duration. Paragraph (ii) controls O2 exposures by 
requiring that diving operations conform to the 24-hour single-exposure 
O2 limits specified in the 2001 NOAA Diving Manual and the 
1995 DSAT report contained in the publication entitled ``Enriched Air 
Operations and Resource Guide.'' In the single comment received on this 
proposed condition (Ex. 5-1), Dr. Raymond expressed concern about the 
deleterious effects of breathing O2 at 1.40 ATA, stating, 
``The risk of oxygen toxicity from Nitrox diving is a * * * very real 
concern. Oxygen-induced seizures usually abate when the high-oxygen gas 
* * * is replaced by air, but any seizure which occurs in the water is 
a potential disaster, placing the diver at risk for AGE, drowning and 
death.'' (Emphasis in original.)
    As noted in the proposal, OSHA agrees that O2 toxicity 
is a substantial hazard to divers breathing nitrox breathing-gas 
mixtures. The Agency is retaining this condition in the final rule as 
proposed because the NOAA and DSAT procedures are designed to protect 
divers by effectively regulating their exposure to O2. 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 of 
these procedures and, as OSHA concluded in granting the Dixie Diver 
variance, both of these procedures afford divers adequate protection 
against O2 toxicity. Moreover, restricting diving operations 
to 130 fsw (see Condition 4(b) below) will provide divers with added 
protection from O2 toxicity.
    (b) Limiting diving depth. Under this proposed condition, employers 
would have to limit divers covered by the amendment to a maximum depth 
of 130 fsw or to a maximum O2 partial pressure of 1.40 ATA, 
whichever exposes them to less O2. OSHA is adopting the 
requirements specified by this proposed condition in the final rule 
because it finds that the condition limits divers'

[[Page 7356]]

overall exposure to O2. In addition, as noted in the 
discussion of Condition 3 above, limiting the depth of diving 
operations also will restrict the partial pressure of oxygen in the 
nitrox breathing-gas mixture, thereby lowering the incidence of 
O2 toxicity.
5. Use of No-Decompression Limits
    (a) No-decompression procedures. In the proposal, this condition 
specified that employers must ensure that divers using nitrox 
breathing-gas mixtures remain within the no-decompression limits 
specified for single and repetitive air diving. These limits are 
available in the 2001 NOAA Diving Manual (Ex. 3-12) or the 1994 DSAT 
report entitled ``Development and Validation of No-Stop Decompression 
Procedures for Recreational Diving: The DSAT Recreational Dive 
Planner'' (Ex. 3-14). In determining the 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. According to NOAA, EAD ``is the depth based 
on the partial pressure of nitrogen in the gas mixture to be breathed, 
rather than the actual depth of the dive'' (Ex. 3-12, p. 15-7).
    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 proposal, OSHA cited comments regarding the efficacy of the EAD 
formula submitted to the record by Dr. Edward D. Thalmann (Ex. 2-7), a 
world-renowned expert in treating diving-related medical emergencies 
among recreational divers. In these comments, Dr. Thalmann asserts that 
research data show that the EAD approach is valid for computing no-
decompression limits for O2 partial pressures as high as 1.5 
ATA. He also 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 Nitrox 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 Nitrox no-decompression diving.''
    OSHA received two comments on the proposed condition. The first 
commenter (Ex. 6-4) stated:

    Nitrox may reduce [DCS] only if you do not allow for more 
uptake[;] by staying longer you have just negated this aspect. [DCS] 
is not merely a subject of ``coming up too fast,[''] but rather [is 
caused by] ``inadequate decompression.'' There is no miracle table/
schedule and [DCS] can and will manifest regardless of the table, 
mix or schedule utilized[]. Current proven tables/schedules have 
risk, but are by no means 100%[.]

    Similarly, the second commenter (Ex. 6-8) claimed that ``the risk 
of [DCS] can be lessened, but only if you use air diving decompression 
procedures while diving on nitrox,'' and ``the use of nitrox or any 
other mixed gas will not reduce the need for recompression chambers if 
the divers do not utilize air diving procedures while diving on oxygen 
enriched gas.''
    The Agency agrees with the first commenter that nitrox may reduce 
DCS. This reduction occurs in part because O2 displaces 
nitrogen in the volume of breathing gas available for use. 
Additionally, Condition 5(a) imposes no-decompression limits on diving 
operations, thereby further reducing the uptake of nitrogen and the 
risk of DCS.
    OSHA concurs with both commenters that no diving table or schedule, 
or breathing high levels O2 instead of compressed air, will 
prevent DCS completely. Accordingly, the purpose of this provision is 
to reduce DCS as a significant risk for the divers covered by this 
final rule.
    The statements made by the second commenter imply that only air-
diving procedures will result in a low level of DCS risk. However, 
DSAT's published research reports (see the proposed rule at 68 FR 1406) 
clearly demonstrate that DSAT adopted its tables of no-decompression 
limits only after extensive laboratory and field testing showed that 
these tables are safe and reliable. Additionally, for its part, NOAA 
did base its no-decompression tables on equivalent air-decompression 
limits, consistent with the recommendations of this commenter. 
Therefore, based on this evidence, the Agency is retaining this 
condition in the final rule as proposed.\5\
---------------------------------------------------------------------------

    \5\ Note that the final rule reverses the designations of 
proposed Conditions 5 and 6 to Conditions 6 and 5, respectively. 
Redesignating proposed Condition 6 as Condition 5 groups it with the 
other conditions (i.e., 3 and 4) that address procedures for 
protecting divers from O2 toxicity and DCS.
---------------------------------------------------------------------------

    (b) Dive-decompression computers. Under this proposed condition, 
employers could use dive-decompression computers designed to regulate 
decompression when the computers use the NOAA or DSAT no-decompression 
limits specified above in Condition 5(a) and provide output that 
reliably represents these limits. OSHA is including the condition in 
the final rule as proposed because the condition provides employers 
with the flexibility to use either manual calculations or dive-
decompression computers to determine no-decompression limits. The 
Agency also 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 will ensure that divers use 
only those no-decompression limits approved under this rulemaking.
6. Mixing and Analyzing the Breathing Gas
    (a) Mixing of breathing gas by the employer. When employers prepare 
the breathing-gas mixture, this proposed condition stated that 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) 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 (Ex. 3-12), or using a filter-membrane system. The Agency is 
adopting this condition as proposed because these requirements provide 
quality control over the processes and techniques commonly used and 
accepted by the diving industry to mix nitrox breathing-gas mixtures.
    (b) Analyzing O2. This proposed condition would require 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. OSHA is including this condition in the 
final rule as proposed. This condition will enable employers to 
accurately assess the proportions of O2 and diluent gas in 
nitrox breathing-gas mixtures, thereby ensuring that divers maintain 
the O2 levels necessary to comply with the 24-hour single-
exposure O2 limits described under Condition 4 above. The 
accuracy requirements specified by these provisions are consistent with 
the accuracy requirements for O2 found in

[[Page 7357]]

other provisions of the final rule, and serve the same purpose 
described for these requirements (see the discussion for proposed 
Condition 2(c) above).
    (c) Commercially supplied breathing gas. This proposed condition 
stated that 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 
``medical-industrial oxygen''). Also, the O2 would have to 
meet the specifications, including the purity requirements, found in 
the ANSI-Compressed Gas Association Commodity Specification for Air, G-
7.1-1997 (ANSI-CGA G7.1-1997). In addition, the employer 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 determined after publication of the proposed rule in the 
Federal Register that it inadvertently misidentified the standard for 
aviator's oxygen and medical-industrial oxygen. In this regard, the 
ANSI-CGA G7.1-1997 does not provide specifications for aviator's 
oxygen, and it lists requirements for medical-grade air, but not for 
medical-grade oxygen. The correct standard for aviator's oxygen and 
medical-grade oxygen is CGA G-4.3-2000 (``Commodity Specification for 
Oxygen'').\6\ The Agency considers this misidentification a technical 
error and is correcting the reference to CGA G-4.3-2000 in the final 
rule. Selecting O2 that meets these specifications ensures 
that divers use the highest quality O2 in their nitrox 
breathing-gas mixtures, thereby preventing them from inhaling 
contaminants. In addition, they require the O2 to have a 
moisture content that helps to maintain normal pulmonary function.
---------------------------------------------------------------------------

    \6\ The aviator's oxygen specification is Type I, Quality 
Verification Level E (Aviator's Breathing Oxygen), while the 
specification for medical-grade oxygen is Type I, Quality 
Verification Level A (Medical USP); see Ex. 3-15, p. 2.
---------------------------------------------------------------------------

    The Agency revised the proposed condition to indicate that the 
requirements specified in paragraphs (i) through (iv) are the 
responsibility of the supplier, not the employer. The Agency also 
combined proposed paragraphs (iii) and (iv) in the final rule to 
simplify the requirements. These paragraphs still specify that the 
accuracy of the method used to analyze O2 must conform to 
the tolerance limits specified under condition (b) above. Additionally, 
employers must ensure that commercial suppliers analyze the breathing-
gas mixture actually contained in the SCUBA cylinders to determine the 
fraction of that the divers will breathe, unaffected by O2 
in the storage banks used to fill the SCUBA cylinders. Also, the 
supplier must provide documentation to the employer specifying the 
analytic procedures used in making the O2 determination and 
the O2 fraction in the charged tanks delivered to the 
employer. OSHA is including these requirements in the final standard to 
provide assurance that the nitrox breathing-gas mixtures supplied to 
divers contain the correct levels of O2, as required by 
Condition 4 above.
    (d) Using a compressor. This proposed condition specified that when 
employers produce nitrox breathing-gas mixtures, and before using a 
compressor in which the gas pressure in any system component exceeds 
125 psi, they must ensure that: (i) Compressor manufacturers 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) compressors are oil-less or oil-free and rated for 
O2 service, unless the employer complies with the 
requirements of condition (e) below; and (iii) compressors meet 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% by volume. In the proposal, OSHA stated that the purpose of 
these proposed requirements was to prevent O2-accelerated 
explosions during the mixing process, the risk of which increases when 
gas pressure in a system component exceeds 125 psi.
    OSHA revised paragraph (i) of this condition to indicate that the 
requirement specified in this paragraph is the responsibility of the 
compressor manufacturer, not the employer, but is adopting paragraph 
(ii) in the final rule as proposed. These provisions will provide 
assurance that a compressor's components cannot serve as an ignition 
source for an O2-accelerated explosion.
    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 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. The Agency finds that these equipment 
requirements, along with the other provisions of this condition, will 
reduce the risk of an O2-accelerated explosion. Therefore, 
OSHA is adopting these requirements in the final rule.
    (e) Oil-lubricated compressors. Before the 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 would require employers 
to: (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.
    Two commenters responded to this proposed condition. The first 
commenter (Ex. 6-5) made the following statement:

    [R]estricting compressor usage based on the [u]nlikely event 
that there would be a fire is preposterous, particularly in the area 
of restricting oil compressors. We know of [no] incidents * * * 
where there was a problem using oil compressors and membrane 
systems. Most membrane systems [never] allow an oxygen content over 
40%. In our case we keep our mixture around 32-33%, and it is not 
possible that this mixture would [cause] a fire. Our air is double 
filtered and our hydrocarbon content is quite low.

    Unfortunately, this commenter did not identify the provisions of 
the proposed condition considered to be ``restricting.'' The commenter 
stated that he already filters the high-pressure air as required under 
this condition by proposed paragraph (iii). The product-certification 
requirements under proposed paragraphs (ii) and (iv) placed the major 
responsibility on the compressor and filter manufacturers. The 
remaining requirements under this condition are the uncontaminated-air 
and continuous-monitoring requirements of proposed paragraphs (i)

[[Page 7358]]

and (v). By maintaining the concentrations of O2 in the 
mixing process at 40% or less, which the commenter already is doing, he 
avoids the additional requirements of paragraphs (i)(1) and (i)(2) of 
Sec. 1910.430 specified above under Condition 6(d)(iii).
    As OSHA noted in the proposal, oil-based lubricants used in 
compressors contain hydrocarbons that can ignite in the presence of an 
enriched O2 environment during the mixing process; such 
ignition may cause an explosion that injures and kills employees. To 
prevent the injuries and death that could result from such explosions, 
the proposed requirements were designed to ensure that the high-
pressure O2 being pumped through the compressor is free of 
combustible hydrocarbons. Therefore, paragraph (i) of the proposed 
condition specified a requirement that employers use hydrocarbon-free 
air when mixing nitrox breathing gases. By obtaining the manufacturer's 
written certification that the compressor is suitable for this purpose, 
as required by paragraph (ii), the employer knows that system 
components exposed to high O2 will be safe for mixing high-
pressure air with the highest O2 fraction used in the nitrox 
breathing-gas mixture. OSHA revised this provision slightly to indicate 
that providing documentation of a compressor's suitability is the 
responsibility of the manufacturer, not the employer.
    The paragraph (iii) requirement to filter the high-pressure air 
when producing O2-compatible breathing gases, and the filter 
system-certification requirement specified by paragraph (iv), also 
ensure that the breathing gas is free of hydrocarbons. In the final 
rule, OSHA revised paragraph (iv) to indicate that providing 
documentation that the filter system is suitable for producing 
O2-compatible air is the responsibility of the manufacturer, 
not the employer. Additionally, the monitoring requirement under 
paragraph (v) would indicate when high-pressure O2 contains 
hydrocarbons, thereby alerting the employer of the need to take 
emergency action (i.e., shut off O2 flow to the compressor 
and then purge the compressor with an inert gas). Paragraph (v) of this 
condition would impose a basic requirement to assure that the final 
nitrox mixture is free of hydrocarbon particulates. OSHA believes the 
elements of the proposed condition are necessary to protect divers, and 
is retaining these conditions in the final standard.
    The president of Machine Design & Fabrication, Inc., Mr. Tom Grubb, 
submitted comments regarding compressors that use synthetic lubricants 
(Ex. 5-3). After noting that most compressors used for mixing breathing 
gases use synthetic lubricants (usually diester or triester based), Mr. 
Grubb argued that the final rule should treat these compressors in the 
same fashion as oil-less or oil-free compressors. In doing so, he 
asserted that compressors that use synthetic lubricants have 
flashpoints and autoignition temperatures that are higher than the 
operating temperatures of the compressors, thereby eliminating the risk 
of hydrocarbon contamination of the breathing gas. He concludes that 
these compressors are as safe as oil-less and oil-free compressors when 
operated according to the manufacturers' specifications regarding 
maximum temperature, cooling, ventilation, and maintenance.
    Mr. Grubb raises an issue regarding the safety of synthetic 
lubricants that OSHA did not address in the proposal. As the regulated 
community has not had an opportunity to comment on this issue, the 
Agency is not in a position at this time to act on Mr. Grubb's 
recommendations. Therefore, for the purposes of the alternative 
procedures permitted by this final rule, employers who operate 
compressors that use synthetic lubricants are to treat these 
compressors in the same fashion as oil-lubricated compressors.
    In addition, Mr. Grubb noted the importance of using compressor 
systems according to the manufacturers' specifications. Under the 
certification requirements in proposed conditions (d)(ii), (e)(ii), and 
(e)(iv), manufacturers are responsible for providing the user with 
information on how to use their equipment safely and appropriately. 
Therefore, the Agency is adding the phrase ``when operated in 
accordance with the manufacturer's operating and maintenance 
specifications'' to these provisions.
    (f) Compliance with other OSHA standards. Under this proposed 
condition, employers must ensure that SCUBA equipment in which either 
nitrox breathing-gas mixtures or pure O2 is under high 
pressure (i.e., exceeding 125 psi) complies with the requirements of 
paragraphs (i)(1) and (i)(2) of Sec. 1910.430. OSHA is including this 
condition in the final standard as proposed because it ensures that 
this equipment is free of ignition sources that could cause an 
O2-accelerated explosion. As noted above in the discussion 
of Condition 3(d)(iii), the Agency believes that paragraphs (i)(1) and 
(i)(2) of Sec. 1910.430 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.\7\
---------------------------------------------------------------------------

    \7\ In addition, employers already are required to comply with 
other OSHA standards that provide for accurate mixing and 
decontamination (especially hydrocarbon removal) of breathing gases, 
and they must assure that employees are properly protected during 
these activities. These standards include the appropriate provisions 
of Sec.Sec. 1910.101 (``Compressed gases (general requirements)''), 
1910.169 (``Air receivers''), and 1910.134 (``Respiratory 
protection'').
---------------------------------------------------------------------------

7. Emergency Egress
    (a) Bail-out system. The proposed condition would require employers 
to equip their divers with a reliable emergency-egress system (i.e., a 
``bail-out system'') for emergencies involving SCUBA malfunctions that 
endanger diver health and safety (e.g., high CO2 levels). 
The bail-out system must contain a separate supply of breathing gas, 
which may include air, and provide the breathing gas to the second 
stage of the SCUBA regulator. OSHA is including this condition in the 
final standard as proposed because the bail-out system enables divers 
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 systems. In the proposal, this condition allowed 
for alternatives to bail-out systems for use with open-circuit SCUBA 
and semi-closed-circuit or closed-circuit rebreathers. Such an 
alternative system would provide the diver with a reserve supply of 
breathing air or gas mixture. When a diver uses open-circuit SCUBA with 
a nitrox breathing-gas mixture, the alternative system permits 
employers to use the emergency-egress procedure (i.e., reserve 
breathing-gas supplies) specified for open-circuit SCUBA by paragraph 
(c)(4) of Sec. 1910.424 instead of a separate bail-out breathing-gas 
system.\8\ For semi-closed-circuit and closed-circuit rebreathers, such 
an alternative system would be configured so that the second stage of 
the regulator connects to a reserve supply of emergency breathing gas.
---------------------------------------------------------------------------

    \8\ Paragraph (c)(4) of Sec. 1910.424 is an emergency-escape 
provision in OSHA's existing CDO standards that applies to divers 
using air-supplied open-circuit SCUBA.
---------------------------------------------------------------------------

    The Agency is adopting the condition in the final rule as proposed. 
In this regard, paragraph (c)(4) of Sec. 1910.424 already recognizes 
the safety afforded to divers by the alternative system used for air-
supplied open-circuit SCUBA diving operations. Therefore, OSHA 
concludes that this alternative system will provide a similar level of 
protection to divers who use open-circuit SCUBA supplied with nitrox 
breathing-gas mixtures. In

[[Page 7359]]

extending this alternative system to semi-closed-circuit and closed-
circuit rebreathers, OSHA believes that any bail-out system that allows 
divers to access a secondary source of sufficient quantities of 
emergency breathing gas will provide them with the requisite level of 
protection during emergency escape. Examples of a secondary source of 
emergency breathing gas include an inflator-regulator system or a 
manual reserve activated by a valve maintained in the closed position 
until needed (as permitted for air-supplied open-circuit SCUBA under 
Sec. 1910.424(c)(4)(i) and (c)(5)).
    (c) Safety requirements. This proposed condition provided that 
employers rely on rebreather manufacturers to specify the necessary 
capacity for a bail-out system because these manufacturers are in the 
best position to make this determination. A rebreather manufacturer can 
determine this capacity based on critical diving parameters (e.g., 
depth of dive and breathing rate) provided by the employer.
    The Agency is including this condition in the final rule as 
proposed because it ensures that the bail-out system used by divers, 
whether it is a separate bail-out system or an alternative bail-out 
system built into the breathing equipment, will function appropriately 
when needed by the diver for emergency egress. A properly functioning 
bail-out system will enable the diver to terminate the dive and make a 
safe and controlled ascent to the surface under emergency conditions, 
thereby preventing over-pressurization of the lungs associated with 
AGE.
8. Treating Diving-Related Medical Emergencies
    (a) Availability of medical resources. As proposed, this condition 
would require employers, prior to beginning diving operations each day, 
to 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. These requirements would avoid 
unnecessary delay in treating diving-related injuries by confirming 
that resources are on call and available to render appropriate 
treatment, by alerting the treatment facility to the occurrence of a 
diving-related medical injury so it can initiate treatment action, and 
by providing timely transportation for the injured diver to the 
treatment facility.
    The Agency received no comments on paragraphs (i) and (ii) of this 
condition. OSHA is adopting these paragraphs as proposed because it 
believes that these provisions will ensure that medical treatment for 
DCS and other diving-related injuries is readily available, thereby 
improving the likelihood that affected divers will recuperate fully 
from these injuries.
    Regarding the two-hour travel-time requirement proposed by 
paragraph (iii) of this condition, the Professional Association of 
Diving Instructors (PADI) recommended that the Agency remove this 
paragraph entirely from the final rule (Exs. 5-2 and 5-2-1). PADI 
justified this recommendation in the following statement:

    The experience of the dive industry since the 1999 Dixie Divers 
variance went into effect has been that while the practice of no-
decompression enriched air diving has expanded significantly, [DCS] 
injuries to professionals at work as a result of the variance have 
not occurred. In fact, PADI's incident reporting system, which 
requires PADI professionals to report any incident of injury that 
they may suffer or witness, has recorded no [DCS] (or other) 
injuries to dive professionals as a result of the variance. PADI 
records show that during this period of time, PADI Instructors have 
certified in excess of 30,000 divers during Enriched Air 
Certification courses, plus had many thousands of exposures using 
enriched air while acting as dive guides.

    PADI also noted that in the preamble to the Dixie Diver variance, 
OSHA ``quoted Dr. Edward D. Thalmann * * *, who clearly stated, `there 
is no rationale for having different requirements for recompression 
chamber availability for air and (n)itrox no-decompression diving.''' 
In conclusion, PADI commented:

    Based upon Dr. Thalmann's previously stated position, and upon 
the experience of PADI Instructors in the field and PADI's incident 
report records, PADI recommends that the proposed condition for 
recompression chamber access as [it] relates to defining a specific 
maximum transport time is unnecessary, and the issue should be 
treated as it is for recreational diving using air, i[.]e., no 
special condition regarding maximum transport time should be 
required.

    As OSHA noted in the proposal, Dr. Thalmann first discussed the 
four-hour travel-time requirement in the context of pain-only DCS and 
DCS with severe neurological symptoms that occur among recreational 
divers during no-decompression dives (Ex. 2-7). In this discussion, Dr. 
Thalmann noted that a treatment delay of four hours can occur without 
diminishing treatment success (i.e., complete relief of symptoms). Dr. 
Thalmann stated further that ``[t]here is no significant body of 
evidence to suggest that, so long as one is diving within accepted no-
decompression limits breathing air or Nitrox, having access to a 
recompression facility within 4 hours is inadequate'' (Ex. 2-7).
    Secondly, Dr. Thalmann concluded that travel time and 
decompression-chamber availability are irrelevant with regard to AGE 
because the incidence of AGE is extremely low among recreational divers 
breathing air supplied by an open-circuit SCUBA. After reviewing 
available research studies and data from the Diver Alert Network 
(``DAN''), Dr. Thalmann concluded that ``[AGE] is a rare occurrence and 
can be avoided with proper training and experience,'' that it ``is 
essentially independent of the time spent 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.'' However, Dr. Larry Raymond stated that ``[t]he treatment for 
[AGE] * * * is immediate pressurization in a recompression chamber. 
Delay compromises the diver's chances of a good outcome'' (Ex. 5-1).\9\
---------------------------------------------------------------------------

    \9\ Dr. Raymond made these comments in reference to an OSHA news 
release (dated January 10, 2003) that stated erroneously that nitrox 
breathing-gas mixtures prevented AGE. Dr. Raymond did indicate 
correctly that nitrox breathing-gas mixtures do not, in fact, 
prevent AGE. OSHA subsequently corrected this news release (with the 
same issue date of January 10, 2003).
---------------------------------------------------------------------------

    In reviewing the AGE-related comments submitted by Drs. Thalmann 
and Raymond, OSHA finds that Dr. Thalmann's comments regarding AGE 
apply directly to recreational-diving operations, while Dr. Raymond did 
not describe the type of diving operations underlying his opinion. In 
addition, Dr. Thalmann based his comments on an extensive analysis of 
recreational divers, while Dr. Raymond did not indicate the specific 
basis for his opinions.
    After carefully reviewing the available information, OSHA is 
revising the two-hour travel-time requirement proposed under paragraph 
(iii) of this condition to four hours in the final rule. The Agency is 
basing this decision on: Dr. Thalmann's comments showing that a four-
hour travel delay is unlikely to impair treatment outcomes for DCS, and 
that AGE is rare among recreational

[[Page 7360]]

divers and can be prevented with proper training and experience; PADI's 
observations regarding the protection afforded to divers by the Dixie 
Diver variance; and the equipment and procedural conditions specified 
in this final rule that are designed to significantly reduce the 
incidence of DCS and AGE.
    (b) O2 treatment. Oxygen treatment is the preferred means of 
initially treating AGE and DCS (Ex. 3-12, pp. 3-19 and 3-28). 
Accordingly, this proposed condition would require employers to ensure 
that portable O2 equipment is available at the dive site to 
treat an injured diver. This equipment would have to deliver medical-
grade O2 (i.e., Type I, Quality Verification Level A 
(medical USP) of CGA G-4.3-2000 (``Commodity Specification for 
Oxygen'')) (Ex. 3-15, p. 2) to a transparent mask that covers the 
injured diver's nose and mouth. Additionally, the equipment must be 
available for this purpose from the time the employer recognizes the 
symptoms of a diving-related medical emergency until the injured diver 
reaches a decompression chamber for treatment.
    OSHA is including this condition in the final rule as proposed 
because it will provide injured divers with the maximum dose of 
O2 possible to enhance treatment effectiveness. Medical-
grade O2 contains minimal contaminates (especially 
hydrocarbons) and adequate moisture to prevent drying of the employee's 
breathing passages and lungs. Also, the transparent mask covering the 
diver's nose and mouth allows attendants to monitor the diver's 
breathing and provides the means to check for an effective seal against 
O2 loss.
    (c) Treatment personnel. This proposed condition specifies that the 
employer, before starting each day's diving operations, must 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 must verify their qualifications before designating them for this 
purpose. The Agency is including this condition in the final standard 
as proposed because personnel qualified in first aid and O2 
treatment will stabilize the 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 this provision is to ensure that properly qualified 
personnel are available for initial treatment, regardless of their 
employment status. However, recognizing that employers may not be 
familiar with the qualifications of non-employees involved in this 
procedure, this provision requires employers to verify their 
qualifications prior to designating them for this purpose.
9. Diving Logs and Decompression Tables
    (a) Diving log. This proposed condition required the employer, 
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 diving and medical terminology and the proper 
procedures for making such entries. Recognizing that many employers of 
recreational divers and diving guides are small businesses that may not 
have an employee available to make entries in the diving log, OSHA also 
proposed under this condition to allow non-employees to make entries in 
the log. The Agency is including this provision in the final rule as 
proposed because it believes that any properly qualified individual can 
make such entries, provided that, as noted earlier, the employer 
verifies their qualifications before designating them for this purpose.
    (b) Diving log requirements. Under this proposed condition, 
employers would have to: (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 according to the provisions of Sec. 1910.440, including the 
requirements for record availability, access to records by employees 
and OSHA, and retention of records. The Agency is retaining this 
condition in the final standard as proposed. Diving logs enable the 
employer to assess the safety of each dive and determine which diving 
parameters are especially hazardous. Should an injury occur during a 
dive, the log allows the employer to inform medical personnel about the 
parameters of the dive that may assist them in making an accurate 
diagnosis of the injury and prescribing an effective treatment. In 
addition, employers covered by this condition must continue to collect 
dive records as required by Sec. 1910.423(d) and meet the other 
recordkeeping provisions of Sec. 1910.440 because their employees 
breathe a mixed gas (i.e., nitrox) during diving operations.
    (c) Availability of decompression tables. As proposed, employers 
must have a hard copy of the no-decompression tables used for the dives 
(see Condition 5(a) above) readily available at the dive site, whether 
or not the divers use dive-decompression computers. OSHA is maintaining 
the requirement in the final rule as proposed because it ensures 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 serves both as a reference source should 
decompression become necessary, and as a back-up resource to divers 
with dive-decompression computers (see Condition 5(b) above).
10. Diver Training
    Under this condition as proposed, employers would have to 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. At a minimum, 
the divers must be trained to: recognize the effects of breathing 
excessive CO2 and O2; take appropriate action 
after detecting the effects of breathing excessive CO2 and 
O2; and properly evaluate, operate, and maintain their 
diving equipment under the diving conditions they encounter.
    This performance-based condition provides assurance that divers are 
trained to perform safely and effectively while using open-circuit 
SCUBAs or rebreathers supplied with nitrox breathing-gas mixtures. 
Although the Agency believes that employers are in the best position to 
determine when the training their divers receive is adequate for this 
purpose, the provision nevertheless specifies several critical tasks, 
as noted above, that divers must perform safely and effectively.
    The Agency is including the condition in the final standard as 
proposed because divers must be able to recognize the life-threatening 
effects of CO2 and O2 toxicity, including 
convulsions and loss of consciousness, and be capable of taking 
remedial actions to prevent and properly respond to them. In addition, 
OSHA believes that if divers know how to evaluate, operate, and 
maintain their open-circuit SCUBAs and rebreathers under the diving 
conditions they encounter, they will be less likely to experience 
equipment failure, thereby reducing the incidence of AGE that may 
result during rapid emergency egress.
11. Testing Protocol for Determining the CO2 Limits of 
Rebreather Canisters
    The proposed condition specified 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

[[Page 7361]]

material is no longer absorbing CO2 effectively (see 
Condition 1(h) above). Employers may use a canister-replacement 
schedule developed by a rebreather manufacturer only when the 
manufacturer has tested the schedule according to the protocol 
specified under this condition.
    The Agency adapted the U.S. Navy Experimental Diving Unit's (NEDU) 
canister-testing protocol (Ex. 3-11) and statistical procedures (Ex. 3-
9) for this rulemaking; the NEDU is the lead Federal agency for testing 
CO2-sorbent replacement schedules. OSHA believes that the 
NEDU protocol provides valid and reliable data for determining 
CO2-sorbent replacement schedules because NEDU carefully 
executed and controlled significant variables that deplete 
CO2-sorbent materials, such as breathing rate (by using 
breathing machines) and ambient temperature. In addition, NEDU conducts 
extensive research and development programs involving canister-duration 
testing (Ex. 3-4, pp. 3-5, 5-12, 9-7 through 9-10, P-34 through P-36, 
and P-69 through P-75).
    (a) Testing the physical properties of the CO2-sorbent material. 
Under this proposed condition, employers would have to ensure that the 
rebreather manufacturer has used the required procedures to determine 
that the CO2-sorbent material has several necessary physical 
properties. These procedures include: (i) The North Atlantic Treaty 
Organization CO2 absorbent-activity test to assess the 
capacity of the material to absorb CO2; (ii) the RoTap 
shaker and nested-sieves test 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.
    The Agency is including the condition in the final standard as 
proposed because it believes that these procedures assure the quality 
of the CO2-sorbent material. They also indicate whether the 
CO2-sorbent material meets the specifications provided by 
the material's manufacturer. In developing the canister-replacement 
schedule using the protocol specified under this condition, rebreather 
manufacturers must approve for use only CO2-sorbent 
materials that meet these specifications. Carefully controlling the 
conditions used to develop a canister-replacement schedule, including 
the quality of the CO2-sorbent material, will ensure that 
the schedule is reliable. Therefore, an employer who has this 
information will be able to replace a diver's canister before the 
CO2-sorbent material fails (i.e., before CO2 
increases to dangerous levels).
    (b) Testing canister function. This proposed condition would 
require employers to ensure that the rebreather manufacturer has used 
the specified canister-testing protocol. The canister-testing protocol 
measures the effects of three factors on canister performance: 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 final rule 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 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 
under the amendment); providing tolerance limits for water 
temperatures; and defining canister duration as the time taken to reach 
0.005 ATA of CO2 (a CO2 partial pressure of 0.005 
ATA is the level specified under Condition 1(e) as the maximum 
allowable amount of CO2 in the breathing gas). In addition, 
the protocol expressly prohibits the employer from using extrapolation 
of the protocol results to establish a CO2-sorbent 
replacement schedule. NEDU's statistical procedures (Ex. 3-9) do not 
provide a method for extrapolating the duration of CO2-
sorbent materials beyond the results obtained during the canister-
testing trials.
    The Agency is including this condition in the final rule as 
proposed to improve the validity and reliability of canister-
replacement schedules. Accordingly, it will enable employers to replace 
CO2-sorbent materials before the sorbent capabilities of 
these materials are depleted.

III. Legal Considerations

    Employers covered by this final rule are currently covered by the 
commercial diving standard. The requirements of that standard are 
protecting their employees from significant risk. In issuing a variance 
from this standard to Dixie Divers, the Agency determined that the 
practices and protections in the variance would provide Dixie Divers' 
recreational diving instructors and diving guides with comparable 
protection to that provided by the decompression-chamber requirements 
of the standard. This final rule extends these alternative protections 
to all such instructors and guides. In this regard, the amendment does 
not totally replace these existing requirements, but instead provides a 
limited alternative to them. OSHA finds that this final rule does not 
directly increase or decrease the protection afforded to employees, nor 
does it increase employers' compliance burdens. As demonstrated in the 
following sections, this amendment likely will 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 final rule.

IV. Final Economic Analysis and Regulatory Flexibility Certification

    This final rule 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 final rule imposes 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.
    Employers of recreational diving instructors and diving guides who 
comply with the conditions in the final rule will be able to expand 
their operations to include nitrox diving, because they will not need 
to purchase and maintain a decompression chamber at the dive site. By 
providing regulatory flexibility to these employers, the final rule may 
reduce their costs and increase productive time. The Agency concludes 
that this final rule does not impose any additional costs on affected 
employers; consequently, the standard requires no final economic 
analysis. Furthermore, because the final rule provides an additional 
voluntary compliance option and, thus, does not impose expenditures on 
any employer, OSHA certifies that the rule does not have a significant 
impact on a substantial number of small entities. Accordingly, the 
Agency did not prepare a final regulatory flexibility analysis.

V. Paperwork Reduction Act

    The final rule contains two collection-of-information (i.e., 
paperwork) requirements: Conditions 9(b)(i) and 9(b)(ii) of Appendix C. 
Condition 9(b)(i) requires employers to ensure that the

[[Page 7362]]

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 according to 
the provisions of Sec. 1910.440 (``Recordkeeping requirements''). 
However, these paperwork requirements already apply to these employers 
under subpart T, regardless of this final rule, because their divers 
are using a mixed-gas (i.e., nitrox) breathing supply. The regulatory 
alternative provided by this final rule 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 OMB Control No. 1218-0069.

VI. Federalism

    The Agency has reviewed this final rule and 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 final rule 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 this rulemaking 
does not expand this limitation.
    This final rule addresses problems that are national in scope. In 
this regard, for employers across the nation whose divers provide 
recreational diving instruction and dive-guiding services, the final 
rule provides an opportunity to safely perform nitrox diving operations 
at a maximum depth of 130 feet of sea water without the expense 
involved in purchasing a decompression chamber. The amendment also 
enables employers in every State 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 O2 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 standards that are identical to OSHA 
standards, or adopt different standards, that are at least as effective 
as the OSHA rule. The final rule only provides employers with an 
alternative to the requirements of the Commercial Diving Operations 
standards. It does not impose additional requirements on employers. 
Accordingly, State-Plan States are not obligated to adopt this final 
rule. Nevertheless, OSHA strongly encourages them to adopt the 
amendment to provide these compliance options to employers in their 
States.

VII. State Plans

    The Agency strongly encourages the 24 States and two Territories 
with their own OSHA-approved occupational safety and health plans to 
revise their current Commercial Diving Operations standards to reflect 
this final rule. 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 continuing to protect the 
safety and health of recreational diving instructors and diving guides. 
These States and Territories are: Alaska, Arizona, California, 
Connecticut (public-sector employees only), Hawaii, Indiana, Iowa, 
Kentucky, Maryland, Michigan, Minnesota, Nevada, New Jersey (public-
sector employees only), New Mexico, New York (public-sector employees 
only), North Carolina, Oregon, Puerto Rico, South Carolina, Tennessee, 
Utah, Vermont, Virginia, Virgin Islands (public-sector employees only), 
Washington, and Wyoming.

VIII. Unfunded Mandates

    OSHA has reviewed this final rule 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 (``Final 
Economic Analysis and Regulatory Flexibility Finding'') of this 
preamble, the Agency has made a determination that this rule imposes no 
regulatory burdens on any employer, either public or private. The 
substantive content of the amendment applies only to employers of 
recreational diving instructors and diving guides, and compliance with 
the amendment is strictly optional for the employers. Accordingly, the 
final rule requires 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, this final rule 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, this final rule 
does not mandate that State, local, and tribal governments adopt new, 
unfunded regulatory obligations.

IX. Applicability of Existing Consensus Standards

    OSHA is not aware of any national consensus standards that are 
similar to this final rule.

List of Subjects in 29 CFR Part 1910

    Health, Occupational safety and health, Safety.

X. Authority and Signature

    This document was prepared under the authority of John L. Henshaw, 
Assistant Secretary of Labor for Occupational Safety and Health, U.S. 
Department of Labor, 200 Constitution Avenue, N.W., Washington, DC 
20210. Accordingly, pursuant to Sections 4, 6, and 8 of the OSH Act of 
1970 (29 U.S.C. 653, 655, 657), Section 107, Contract Work Hours and 
Safety Standards Act (the Construction Safety Act) (40 U.S.C. 333), 
Section 41, Longshore and Harbor Workers' Compensation Act (33 U.S.C. 
941), Secretary of Labor's Order No. 5-2002 (67 FR 65008), and 29 CFR 
part 1911, OSHA is hereby amending subpart T of 29 CFR part 1910 as set 
forth below.


[[Page 7363]]


    Signed at Washington, DC on February 10, 2004.
John L. Henshaw,
Assistant Secretary of Labor.

XI. Amendment to Standard

0
For the reasons stated in the preamble, the Agency is amending 29 CFR 
part 1910, subpart T as follows:

PART 1910--[AMENDED]

Subpart T--[Amended]

0
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); Section 107, 
Contract Work Hours and Safety Standards Act (the Construction 
Safety Act) (40 U.S.C. 333); Section 41, Longshore and Harbor 
Workers' Compensation Act (33 U.S.C. 941); Secretary of Labor's 
Order No. 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.

0
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 are not required to comply with the decompression-chamber 
requirements specified by paragraphs (b)(2) and (c)(3)(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.
* * * * *

0
3. Add new definitions for ``dive-guiding operations'' and 
``recreational diving instruction'' to the alphabetical list of 
definitions in Sec. 1910.402, to read as follows:


Sec. 1910.402  Definitions.

    Dive-guiding operations means leading groups of sports divers, who 
use an open-circuit, semi-closed-circuit, or closed-circuit self-
contained underwater breathing apparatus, 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 an open-circuit, semi-closed-circuit, or 
closed-circuit self-contained underwater breathing apparatus, during 
dives.
* * * * *

0
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 an employer of 
recreational diving instructors and diving guides (hereafter, 
``divers'' or ``employees'') who complies with all of the conditions 
of this appendix need not provide a decompression chamber for these 
divers as required under Sec.Sec. 1910.423(b)(2) or (c)(3) or 
1910.426(b)(1).

1. Equipment Requirements for Rebreathers

    (a) The employer must ensure that each employee operates the 
rebreather (i.e., semi-closed-circuit and closed-circuit self-
contained underwater breathing apparatuses (hereafter, ``SCUBAs'')) 
according to the rebreather manufacturer's instructions.
    (b) The employer must ensure that each rebreather has a 
counterlung that supplies a sufficient volume of breathing gas to 
their divers to sustain the divers' respiration rates, and contains 
a baffle system and/or other moisture separating system that keeps 
moisture from entering the scrubber.
    (c) The employer 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) Each employee uses the moisture trap according to the 
rebreather manufacturer's instructions.
    (d) The employer 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 diver under the diving conditions in which 
the diver operates, and warns the diver of moisture in the breathing 
loop in sufficient time to terminate the dive and return safely to 
the surface; and
    (ii) Each diver uses the moisture sensor according to the 
rebreather manufacturer's instructions.
    (e) The employer must 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 each 
diver under the diving conditions in which the diver operates; and
    (iii) The CO2 alarm remains continuously activated 
when the inhaled CO2 level reaches and exceeds 0.005 
atmospheres absolute (ATA).
    (f) Before each day's diving operations, and more often when 
necessary, the employer 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) The equipment and procedures 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) The employer must replace the CO2 sensor when it 
fails to meet the accuracy requirements specified in paragraph 
1(f)(iii) of this appendix, and ensure that the replacement 
CO2 sensor meets the accuracy requirements specified in 
paragraph 1(f)(iii) of this appendix before placing the rebreather 
in operation.
    (h) As an alternative to using a continuously functioning 
CO2 sensor, the employer may use a schedule for replacing 
CO2-sorbent material provided by the rebreather 
manufacturer. The employer may use such a schedule only when the 
rebreather manufacturer has developed it according to the canister-
testing protocol specified below in Condition 11, and must use the 
canister within the temperature range for which the manufacturer 
conducted its scrubber canister tests following that protocol. 
Variations above or below the range are acceptable only after the 
manufacturer adds that lower or higher temperature to the protocol.
    (i) When using CO2-sorbent replacement schedules, the 
employer 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 ATA.
    (j) As an alternative to manufactured, disposable scrubber 
cartridges, the employer may fill CO2 scrubber cartridges 
manually with CO2-sorbent material when:
    (i) The rebreather manufacturer permits manual filling of 
scrubber cartridges;

[[Page 7364]]

    (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) of this 
appendix; and
    (iv) The employer demonstrates that manual filling meets the 
requirements specified in paragraph 1(i) of this appendix.
    (k) The employer must ensure that each rebreather has an 
information module that provides:
    (i) A visual (e.g., digital, graphic, analog) or auditory (e.g., 
voice, pure tone) display that effectively warns the diver of 
solenoid failure (when the rebreather uses solenoids) and other 
electrical weaknesses or failures (e.g., low battery voltage);
    (ii) For a semi-closed circuit rebreather, a visual display for 
the partial pressure of CO2, or deviations above and 
below a preset CO2 partial pressure of 0.005 ATA; and
    (iii) For a closed-circuit rebreather, a visual display 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 or 
lower; gas temperature in the breathing loop; and water temperature.
    (l) Before each day's diving operations, and more often when 
necessary, the employer must ensure that the electrical power supply 
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) The employer must ensure that each closed-circuit rebreather 
uses 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) The employer must 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, the employer must calibrate O2 sensors as 
required by the sensor manufacturer's instructions. In doing so, the 
employer 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 in paragraph 2(c)(iii) of this 
appendix; and
    (v) Ensure that the replacement O2 sensors meet the 
accuracy requirements specified in paragraph 2(c)(iii) of this 
appendix before placing a rebreather in operation.
    (d) The employer must ensure that each closed-circuit rebreather 
has:
    (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

    The employer 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 O2 
partial pressure of 1.40 ATA, whichever exposes divers to less 
O2; and
    (c) For a rebreather, never exceeds a maximum O2 
partial pressure of 1.40 ATA.

4. Regulating O2 Exposures and Diving Depth

    (a) Regarding O2 exposure, the employer must:
    (i) Ensure that the exposure of each diver 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 Resource Guide'' published in 1995 by the 
Professional Association of Diving Instructors (known commonly as 
the ``1995 DSAT Oxygen Exposure Table''); 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, the employer must 
ensure that no diver exceeds a depth of 130 feet of sea water 
(``fsw'') or a maximum O2 partial pressure of 1.40 ATA, 
whichever exposes the diver to less O2.

5. Use of No-Decompression Limits

    (a) For diving conducted while using nitrox breathing-gas 
mixtures, the employer must ensure that each diver 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'').
    (b) An employer may permit a diver to use a dive-decompression 
computer designed to regulate decompression when the dive-
decompression computer uses the no-decompression limits specified in 
paragraph 5(a) of this appendix, and provides output that reliably 
represents those limits.

6. Mixing and Analyzing the Breathing Gas

    (a) The employer 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, the 
employer must determine the O2 fraction of the breathing-
gas mixture using an O2 analyzer. In doing so, the 
employer must:
    (i) Ensure that the O2 analyzer is accurate to within 
1% of the O2 fraction by volume.
    (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, the employer must ensure that the 
O2 meets the medical USP specifications (Type I, Quality 
Verification Level A) or aviator's breathing-oxygen specifications 
(Type I, Quality Verification Level E) of CGA G-4.3-2000 
(``Commodity Specification for Oxygen''). In addition, the 
commercial supplier must:
    (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) Include documentation of the O2-analysis 
procedures and the O2 fraction when delivering the 
charged tanks to the employer.
    (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), the:
    (i) Compressor manufacturer must provide the employer with 
documentation that the compressor is suitable for mixing high-
pressure air with the highest O2 fraction used in the 
nitrox breathing-gas mixture when operated according to the 
manufacturer's operating and maintenance specifications;
    (ii) Employer must comply with paragraph 6(e) of this appendix, 
unless the compressor is rated for O2 service and is oil-
less or oil-free; and
    (iii) Employer must 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%.
    (e) Before producing 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, the:
    (i) Employer must use only uncontaminated air (i.e., air 
containing no hydrocarbon particulates) for the nitrox breathing-gas 
mixture;
    (ii) Compressor manufacturer must provide the employer with 
documentation that the compressor is suitable for mixing the high-
pressure air with the highest O2 fraction used in the 
nitrox breathing-gas mixture when operated according to the 
manufacturer's operating and maintenance specifications;

[[Page 7365]]

    (iii) Employer must filter the high-pressure air to produce 
O2-compatible air;
    (iv) The filter-system manufacturer must provide the employer 
with documentation that the filter system used for this purpose is 
suitable for producing O2-compatible air when operated 
according to the manufacturer's operating and maintenance 
specifications; and
    (v) Employer must continuously monitor the air downstream from 
the filter for hydrocarbon contamination.
    (f) The employer must 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.

7. Emergency Egress

    (a) Regardless of the type of diving equipment used by a diver 
(i.e., open-circuit SCUBA or rebreathers), the employer must ensure 
that the equipment contains (or incorporates) 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) As an alternative to the ``bail-out'' system specified in 
paragraph 7(a) of this appendix, the employer may use:
    (i) For open-circuit SCUBA, an emergency-egress system as 
specified in Sec. 1910.424(c)(4); or
    (ii) For a semi-closed-circuit and closed-circuit rebreather, a 
system configured so that the second stage of the regulator connects 
to a reserve supply of emergency breathing gas.
    (c) The employer must obtain from the rebreather manufacturer 
sufficient information to ensure that the bail-out system performs 
reliably and has sufficient capacity 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, the employer 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 four (4) hours travel time 
from the dive site.
    (b) The employer must ensure that portable O2 
equipment is available at the dive site to treat injured divers. In 
doing so, the employer 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, the employer 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 No-Decompression Tables

    (a) Before starting each day's diving operations, the employer 
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) The employer must:
    (i) Ensure that the diving log conforms to the requirements 
specified by paragraph (d) (``Record of dive'') of Sec. 1910.423; 
and
    (ii) Maintain a record of the dive according to Sec. 1910.440 
(``Recordkeeping requirements'').
    (c) The employer must ensure that a hard-copy of the no-
decompression tables used for the dives (as specified in paragraph 
6(a) of this appendix) is readily available at the dive site, 
whether or not the divers use dive-decompression computers.

10. Diver Training

    The employer must ensure that each diver receives training that 
enables the diver to perform work safely and effectively while using 
open-circuit SCUBAs or rebreathers supplied with nitrox breathing-
gas mixtures. Accordingly, each diver must be able to demonstrate 
the ability to 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) The employer must ensure that the rebreather manufacturer 
has used the following procedures for determining that the 
CO2-sorbent material meets the specifications of the 
sorbent material's manufacturer:
    (i) The North Atlantic Treating Organization CO2 
absorbent-activity test;
    (ii) The RoTap shaker and nested-sieves test;
    (iii) The Navy Experimental Diving Unit (``NEDU'')-derived 
Schlegel test; and
    (iv) The NEDU MeshFit software.
    (b) The employer must ensure that the rebreather manufacturer 
has applied the following canister-testing materials, methods, 
procedures, and statistical analyses:
    (i) Use of 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, use of 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) Measurement of the O2 concentration of the 
inhalation breathing gas delivered to the mouthpiece;
    (iv) Testing of the canisters using the three ventilation rates 
listed in Table I below (with the required breathing-machine tidal 
volumes and frequencies, and CO2-injection rates, 
provided for each ventilation rate):

                                      Table I.--Canister Testing Parameters
----------------------------------------------------------------------------------------------------------------
                                                                        Breathing machine
       Ventilation rates (Lpm, ATPS \1\)          Breathing machine        frequencies       CO2 injection rates
                                                  tidal volumes (L)    (breaths per min.)      (Lpm, 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, 
addition of the appropriate combinations of ventilation rates and 
CO2-injection rates;
    (vi) Performance of the CO2 injection at a constant 
(steady) and continuous rate during each testing trial;

[[Page 7366]]

    (vii) Determination of 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) Monitoring of the breathing-gas temperature at the 
rebreather mouthpiece (at the ``chrome T'' connector), and ensuring 
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; \1\
---------------------------------------------------------------------------

    \1\ 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) Implementation of at least eight (8) testing trials for 
each combination of temperature and ventilation-CO2-
injection rates (for example, 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) Allowing 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) Use of 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) Analysis of the canister-duration results using the 
repeated-measures statistics described in NEDU Report 2-99;
    (xiii) Specification of the replacement schedule for the 
CO2-sorbent materials in terms of the lower prediction 
line (or limit) of the 95% confidence interval; and
    (xiv) Derivation of replacement schedules only by interpolating 
among, but not by extrapolating beyond, the depth, water 
temperatures, and exercise levels used during canister testing.

[FR Doc. 04-3289 Filed 2-13-04; 8:45 am]
BILLING CODE 4510-26-P