[Title 29 CFR 1910.399]
[Code of Federal Regulations (annual edition) - July 1, 2002 Edition]
[Title 29 - LABOR]
[Subtitle B - Regulations Relating to Labor (Continued)]
[Subpart S - Electrical]
[Sec. 1910.399 - Definitions applicable to this subpart.]
[From the U.S. Government Printing Office]

29LABOR52002-07-012002-07-01falseDefinitions applicable to this subpart.1910.399Sec. 1910.399LABORRegulations Relating to Labor (Continued)OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENTOCCUPATIONAL SAFETY AND HEALTH STANDARDSElectrical
Sec. 1910.399  Definitions applicable to this subpart.

    Acceptable. An installation or equipment is acceptable to the 
Assistant Secretary of Labor, and approved within the meaning of this 
Subpart S:
    (i) If it is accepted, or certified, or listed, or labeled, or 
otherwise determined to be safe by a nationally recognized testing 
laboratory; or
    (ii) With respect to an installation or equipment of a kind which no 
nationally recognized testing laboratory accepts, certifies, lists, 
labels, or determines to be safe, if it is inspected or tested by 
another Federal agency, or by a State, municipal, or other local 
authority responsible for enforcing occupational safety provisions of 
the National Electrical Code and found in compliance with the provisions 
of the National Electrical Code as applied in this subpart; or
    (iii) With respect to custom-made equipment or related installations 
which are designed, fabricated for, and intended for use by a particular 
customer, if it is determined to be safe for its intended use by its 
manufacturer on

[[Page 868]]

the basis of test data which the employer keeps and makes available for 
inspection to the Assistant Secretary and his authorized 
representatives. Refer to Sec. 1910.7 for definition of nationally 
recognized testing laboratory.
    Accepted. An installation is ``accepted'' if it has been inspected 
and found by a nationally recognized testing laboratory to conform to 
specified plans or to procedures of applicable codes.
    Accessible. (As applied to wiring methods.) Capable of being removed 
or exposed without damaging the building structure or finish, or not 
permanently closed in by the structure or finish of the building. (See 
``concealed'' and ``exposed.'')
    Accessible. (As applied to equipment.) Admitting close approach; not 
guarded by locked doors, elevation, or other effective means. (See 
``Readily accessible.'')
    Ampacity. Current-carrying capacity of electric conductors expressed 
in amperes.
    Appliances. Utilization equipment, generally other than industrial, 
normally built in standardized sizes or types, which is installed or 
connected as a unit to perform one or more functions such as clothes 
washing, air conditioning, food mixing, deep frying, etc.
    Approved. Acceptable to the authority enforcing this subpart. The 
authority enforcing this subpart is the Assistant Secretary of Labor for 
Occupational Safety and Health. The definition of ``acceptable'' 
indicates what is acceptable to the Assistant Secretary of Labor, and 
therefore approved within the meaning of this Subpart.
    Approved for the purpose. Approved for a specific purpose, 
environment, or application described in a particular standard 
    Suitability of equipment or materials for a specific purpose, 
environment or application may be determined by a nationally recognized 
testing laboratory, inspection agency or other organization concerned 
with product evaluation as part of its listing and labeling program. 
(See ``Labeled'' or ``Listed.'')
    Armored cable. Type AC armored cable is a fabricated assembly of 
insulated conductors in a flexible metallic enclosure.
    Askarel. A generic term for a group of nonflammable synthetic 
chlorinated hydrocarbons used as electrical insulating media. Askarels 
of various compositional types are used. Under arcing conditions the 
gases produced, while consisting predominantly of noncombustible 
hydrogen chloride, can include varying amounts of combustible gases 
depending upon the askarel type.
    Attachment plug (Plug cap) (Cap). A device which, by insertion in a 
receptacle, establishes connection between the conductors of the 
attached flexible cord and the conductors connected permanently to the 
    Automatic. Self-acting, operating by its own mechanism when actuated 
by some impersonal influence, as, for example, a change in current 
strength, pressure, temperature, or mechanical configuration.
    Bare conductor. See ``Conductor.''
    Bonding. The permanent joining of metallic parts to form an 
electrically conductive path which will assure electrical continuity and 
the capacity to conduct safely any current likely to be imposed.
    Bonding jumper. A reliable conductor to assure the required 
electrical conductivity between metal parts required to be electrically 
    Branch circuit. The circuit conductors between the final overcurrent 
device protecting the circuit and the outlet(s).
    Building. A structure which stands alone or which is cut off from 
adjoining structures by fire walls with all openings therein protected 
by approved fire doors.
    Cabinet. An enclosure designed either for surface or flush mounting, 
and provided with a frame, mat, or trim in which a swinging door or 
doors are or may be hung.
    Cable tray system. A cable tray system is a unit or assembly of 
units or sections, and associated fittings, made of metal or other 
noncombustible materials forming a rigid structural system used to 
support cables. Cable tray systems include ladders, troughs, channels, 
solid bottom trays, and other similar structures.
    Cablebus. Cablebus is an approved assembly of insulated conductors 

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fittings and conductor terminations in a completely enclosed, 
ventilated, protective metal housing.
    Center pivot irrigation machine. A center pivot irrigation machine 
is a multi-motored irrigation machine which revolves around a central 
pivot and employs alignment switches or similar devices to control 
individual motors.
    Certified. Equipment is ``certified'' if it (a) has been tested and 
found by a nationally recognized testing laboratory to meet nationally 
recognized standards or to be safe for use in a specified manner, or (b) 
is of a kind whose production is periodically inspected by a nationally 
recognized testing laboratory, and (c) it bears a label, tag, or other 
record of certification.
    Circuit breaker. (i) (600 volts nominal, or less). A device designed 
to open and close a circuit by nonautomatic means and to open the 
circuit automatically on a predetermined overcurrent without injury to 
itself when properly applied within its rating.
    (ii) (Over 600 volts, nominal). A switching device capable of 
making, carrying, and breaking currents under normal circuit conditions, 
and also making, carrying for a specified time, and breaking currents 
under specified abnormal circuit conditions, such as those of short 
    Class I locations. Class I locations are those in which flammable 
gases or vapors are or may be present in the air in quantities 
sufficient to produce explosive or ignitible mixtures. Class I locations 
include the following:
    (i) Class I, Division 1. A Class I, Division 1 location is a 
location: (a) in which hazardous concentrations of flammable gases or 
vapors may exist under normal operating conditions; or (b) in which 
hazardous concentrations of such gases or vapors may exist frequently 
because of repair or maintenance operations or because of leakage; or 
(c) in which breakdown or faulty operation of equipment or processes 
might release hazardous concentrations of flammable gases or vapors, and 
might also cause simultaneous failure of electric equipment.
    Note: This classification usually includes locations where volatile 
flammable liquids or liquefied flammable gases are transferred from one 
container to another; interiors of spray booths and areas in the 
vicinity of spraying and painting operations where volatile flammable 
solvents are used; locations containing open tanks or vats of volatile 
flammable liquids; drying rooms or compartments for the evaporation of 
flammable solvents; locations containing fat and oil extraction 
equipment using volatile flammable solvents; portions of cleaning and 
dyeing plants where flammable liquids are used; gas generator rooms and 
other portions of gas manufacturing plants where flammable gas may 
escape; inadequately ventilated pump rooms for flammable gas or for 
volatile flammable liquids; the interiors of refrigerators and freezers 
in which volatile flammable materials are stored in open, lightly 
stoppered, or easily ruptured containers; and all other locations where 
ignitible concentrations of flammable vapors or gases are likely to 
occur in the course of normal operations.
    (ii) Class I, Division 2. A Class I, Division 2 location is a 
location: (a) in which volatile flammable liquids or flammable gases are 
handled, processed, or used, but in which the hazardous liquids, vapors, 
or gases will normally be confined within closed containers or closed 
systems from which they can escape only in case of accidental rupture or 
breakdown of such containers or systems, or in case of abnormal 
operation of equipment; or (b) in which hazardous concentrations of 
gases or vapors are normally prevented by positive mechanical 
ventilation, and which might become hazardous through failure or 
abnormal operations of the ventilating equipment; or (c) that is 
adjacent to a Class I, Division 1 location, and to which hazardous 
concentrations of gases or vapors might occasionally be communicated 
unless such communication is prevented by adequate positive-pressure 
ventilation from a source of clean air, and effective safeguards against 
ventilation failure are provided.
    Note: This classification usually includes locations where volatile 
flammable liquids or flammable gases or vapors are used, but which would 
become hazardous only in case of an accident or of some unusual 
operating condition. The quantity of flammable material that might 
escape in case of accident, the adequacy of ventilating equipment, the 
total area involved, and the record of the industry or business with 
respect to explosions or fires are all factors that merit consideration 
in determining the classification and extent of each location.

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    Piping without valves, checks, meters, and similar devices would not 
ordinarily introduce a hazardous condition even though used for 
flammable liquids or gases. Locations used for the storage of flammable 
liquids or a liquefied or compressed gases in sealed containers would 
not normally be considered hazardous unless also subject to other 
hazardous conditions.
    Electrical conduits and their associated enclosures separated from 
process fluids by a single seal or barrier are classed as a Division 2 
location if the outside of the conduit and enclosures is a nonhazardous 
    Class II locations. Class II locations are those that are hazardous 
because of the presence of combustible dust. Class II locations include 
the following:
    (i) Class II, Division 1. A Class II, Division 1 location is a 
location: (a) In which combustible dust is or may be in suspension in 
the air under normal operating conditions, in quantities sufficient to 
produce explosive or ignitible mixtures; or (b) where mechanical failure 
or abnormal operation of machinery or equipment might cause such 
explosive or ignitible mixtures to be produced, and might also provide a 
source of ignition through simultaneous failure of electric equipment, 
operation of protection devices, or from other causes, or (c) in which 
combustible dusts of an electrically conductive nature may be present.
    Note: This classification may include areas of grain handling and 
processing plants, starch plants, sugar-pulverizing plants, malting 
plants, hay-grinding plants, coal pulverizing plants, areas where metal 
dusts and powders are produced or processed, and other similar locations 
which contain dust producing machinery and equipment (except where the 
equipment is dust-tight or vented to the outside). These areas would 
have combustible dust in the air, under normal operating conditions, in 
quantities sufficient to produce explosive or ignitible mixtures. 
Combustible dusts which are electrically nonconductive include dusts 
produced in the handling and processing of grain and grain products, 
pulverized sugar and cocoa, dried egg and milk powders, pulverized 
spices, starch and pastes, potato and woodflour, oil meal from beans and 
seed, dried hay, and other organic materials which may produce 
combustible dusts when processed or handled. Dusts containing magnesium 
or aluminum are particularly hazardous and the use of extreme caution is 
necessary to avoid ignition and explosion.
    (ii) Class II, Division 2. A Class II, Division 2 location is a 
location in which: (a) combustible dust will not normally be in 
suspension in the air in quantities sufficient to produce explosive or 
ignitible mixtures, and dust accumulations are normally insufficient to 
interfere with the normal operation of electrical equipment or other 
apparatus; or (b) dust may be in suspension in the air as a result of 
infrequent malfunctioning of handling or processing equipment, and dust 
accumulations resulting therefrom may be ignitible by abnormal operation 
or failure of electrical equipment or other apparatus.
    Note: This classification includes locations where dangerous 
concentrations of suspended dust would not be likely but where dust 
accumulations might form on or in the vicinity of electric equipment. 
These areas may contain equipment from which appreciable quantities of 
dust would escape under abnormal operating conditions or be adjacent to 
a Class II Division 1 location, as described above, into which an 
explosive or ignitible concentration of dust may be put into suspension 
under abnormal operating conditions.
    Class III locations. Class III locations are those that are 
hazardous because of the presence of easily ignitible fibers or flyings 
but in which such fibers or flyings are not likely to be in suspension 
in the air in quantities sufficient to produce ignitible mixtures. Class 
III locations include the following:
    (i) Class III, Division 1. A Class III, Division 1 location is a 
location in which easily ignitible fibers or materials producing 
combustible flyings are handled, manufactured, or used.
    Note: Such locations usually include some parts of rayon, cotton, 
and other textile mills; combustible fiber manufacturing and processing 
plants; cotton gins and cotton-seed mills; flax-processing plants; 
clothing manufacturing plants; woodworking plants, and establishments; 
and industries involving similar hazardous processes or conditions.
    Easily ignitible fibers and flyings include rayon, cotton (including 
cotton linters and cotton waste), sisal or henequen, istle, jute, hemp, 
tow, cocoa fiber, oakum, baled waste kapok, Spanish moss, excelsior, and 
other materials of similar nature.
    (ii) Class III, Division 2. A Class III, Division 2 location is a 
location in which easily ignitible fibers are stored or handled, except 
in process of manufacture.
    Collector ring. A collector ring is an assembly of slip rings for 
transferring electrical energy from a stationary to a rotating member.

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    Concealed. Rendered inaccessible by the structure or finish of the 
building. Wires in concealed raceways are considered concealed, even 
though they may become accessible by withdrawing them. [See Accessible. 
(As applied to wiring methods.)]
    Conductor. (i) Bare. A conductor having no covering or electrical 
insulation whatsoever.
    (ii) Covered. A conductor encased within material of composition or 
thickness that is not recognized as electrical insulation.
    (iii) Insulated. A conductor encased within material of composition 
and thickness that is recognized as electrical insulation.
    Conduit body. A separate portion of a conduit or tubing system that 
provides access through a removable cover(s) to the interior of the 
system at a junction of two or more sections of the system or at a 
terminal point of the system. Boxes such as FS and FD or larger cast or 
sheet metal boxes are not classified as conduit bodies.
    Controller. A device or group of devices that serves to govern, in 
some predetermined manner, the electric power delivered to the apparatus 
to which it is connected.
    Cooking unit, counter-mounted. A cooking appliance designed for 
mounting in or on a counter and consisting of one or more heating 
elements, internal wiring, and built-in or separately mountable 
controls. (See Oven, wall-mounted.)
    Covered conductor. See Conductor.
    Cutout. (Over 600 volts, nominal.) An assembly of a fuse support 
with either a fuseholder, fuse carrier, or disconnecting blade. The 
fuseholder or fuse carrier may include a conducting element (fuse link), 
or may act as the disconnecting blade by the inclusion of a nonfusible 
    Cutout box. An enclosure designed for surface mounting and having 
swinging doors or covers secured directly to and telescoping with the 
walls of the box proper. (See Cabinet.)
    Damp location. See Location.
    Dead front. Without live parts exposed to a person on the operating 
side of the equipment.
    Device. A unit of an electrical system which is intended to carry 
but not utilize electric energy.
    Dielectric heating. Dielectric heating is the heating of a nominally 
insulating material due to its own dielectric losses when the material 
is placed in a varying electric field.
    Disconnecting means. A device, or group of devices, or other means 
by which the conductors of a circuit can be disconnected from their 
source of supply.
    Disconnecting (or Isolating) switch. (Over 600 volts, nominal.) A 
mechanical switching device used for isolating a circuit or equipment 
from a source of power.
    Dry location. See Location.
    Electric sign. A fixed, stationary, or portable self-contained, 
electrically illuminated utilization equipment with words or symbols 
designed to convey information or attract attention.
    Enclosed. Surrounded by a case, housing, fence or walls which will 
prevent persons from accidentally contacting energized parts.
    Enclosure. The case or housing of apparatus, or the fence or walls 
surrounding an installation to prevent personnel from accidentally 
contacting energized parts, or to protect the equipment from physical 
    Equipment. A general term including material, fittings, devices, 
appliances, fixtures, apparatus, and the like, used as a part of, or in 
connection with, an electrical installation.
    Equipment grounding conductor. See Grounding conductor, equipment.
    Explosion-proof apparatus. Apparatus enclosed in a case that is 
capable of withstanding an explosion of a specified gas or vapor which 
may occur within it and of preventing the ignition of a specified gas or 
vapor surrounding the enclosure by sparks, flashes, or explosion of the 
gas or vapor within, and which operates at such an external temperature 
that it will not ignite a surrounding flammable atmosphere.
    Exposed. (As applied to live parts.) Capable of being inadvertently 
touched or approached nearer than a safe distance by a person. It is 
applied to parts not suitably guarded, isolated, or insulated. (See 
Accessible. and Concealed.)

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    Exposed. (As applied to wiring methods.) On or attached to the 
surface or behind panels designed to allow access. [See Accessible. (As 
applied to wiring methods.)]
    Exposed. (For the purposes of Sec. 1910.308(e), Communications 
systems.) Where the circuit is in such a position that in case of 
failure of supports or insulation, contact with another circuit may 
    Externally operable. Capable of being operated without exposing the 
operator to contact with live parts.
    Feeder. All circuit conductors between the service equipment, or the 
generator switchboard of an isolated plant, and the final branch-circuit 
overcurrent device.
    Fitting. An accessory such as a locknut, bushing, or other part of a 
wiring system that is intended primarily to perform a mechanical rather 
than an electrical function.
    Fuse. (Over 600 volts, nominal.) An overcurrent protective device 
with a circuit opening fusible part that is heated and severed by the 
passage of overcurrent through it. A fuse comprises all the parts that 
form a unit capable of performing the prescribed functions. It may or 
may not be the complete device necessary to connect it into an 
electrical circuit.
    Ground. A conducting connection, whether intentional or accidental, 
between an electrical circuit or equipment and the earth, or to some 
conducting body that serves in place of the earth.
    Grounded. Connected to earth or to some conducting body that serves 
in place of the earth.
    Grounded, effectively. (Over 600 volts, nominal.) Permanently 
connected to earth through a ground connection of sufficiently low 
impedance and having sufficient ampacity that ground fault current which 
may occur cannot build up to voltages dangerous to personnel.
    Grounded conductor. A system or circuit conductor that is 
intentionally grounded.
    Grounding conductor. A conductor used to connect equipment or the 
grounded circuit of a wiring system to a grounding electrode or 
    Grounding conductor, equipment. The conductor used to connect the 
non-current-carrying metal parts of equipment, raceways, and other 
enclosures to the system grounded conductor and/or the grounding 
electrode conductor at the service equipment or at the source of a 
separately derived system.
    Grounding electrode conductor. The conductor used to connect the 
grounding electrode to the equipment grounding conductor and/or to the 
grounded conductor of the circuit at the service equipment or at the 
source of a separately derived system.
    Ground-fault circuit-interrupter. A device whose function is to 
interrupt the electric circuit to the load when a fault current to 
ground exceeds some predetermined value that is less than that required 
to operate the overcurrent protective device of the supply circuit.
    Guarded. Covered, shielded, fenced, enclosed, or otherwise protected 
by means of suitable covers, casings, barriers, rails, screens, mats, or 
platforms to remove the likelihood of approach to a point of danger or 
contact by persons or objects.
    Health care facilities. Buildings or portions of buildings and 
mobile homes that contain, but are not limited to, hospitals, nursing 
homes, extended care facilities, clinics, and medical and dental 
offices, whether fixed or mobile.
    Heating equipment. For the purposes of Sec. 1910.306(g), the term 
heating equipment includes any equipment used for heating purposes if 
heat is generated by induction or dielectric methods.
    Hoistway. Any shaftway, hatchway, well hole, or other vertical 
opening or space in which an elevator or dumbwaiter is designed to 
    Identified. Identified, as used in reference to a conductor or its 
terminal, means that such conductor or terminal can be readily 
recognized as grounded.
    Induction heating. Induction heating is the heating of a nominally 
conductive material due to its own I\2\R losses when the material is 
placed in a varying electromagnetic field.
    Insulated conductor. See Conductor.
    Interrupter switch. (Over 600 volts, nominal.) A switch capable of 
making, carrying, and interrupting specified currents.

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    Irrigation machine. An irrigation machine is an electrically driven 
or controlled machine, with one or more motors, not hand portable, and 
used primarily to transport and distribute water for agricultural 
    Isolated. Not readily accessible to persons unless special means for 
access are used.
    Isolated power system. A system comprising an isolating transformer 
or its equivalent, a line isolation monitor, and its ungrounded circuit 
    Labeled. Equipment is labeled if there is attached to it a label, 
symbol, or other identifying mark of a nationally recognized testing 
laboratory which, (a) makes periodic inspections of the production of 
such equipment, and (b) whose labeling indicates compliance with 
nationally recognized standards or tests to determine safe use in a 
specified manner.
    Lighting outlet. An outlet intended for the direct connection of a 
lampholder, a lighting fixture, or a pendant cord terminating in a 
    Line-clearance tree trimming. The pruning, trimming, repairing, 
maintaining, removing, or clearing of trees or cutting of brush that is 
within 10 feet (305 cm) of electric supply lines and equipment.
    Listed. Equipment is listed if it is of a kind mentioned in a list 
which, (a) is published by a nationally recognized laboratory which 
makes periodic inspection of the production of such equipment, and (b) 
states such equipment meets nationally recognized standards or has been 
tested and found safe for use in a specified manner.
    Location--(i) Damp location. Partially protected locations under 
canopies, marquees, roofed open porches, and like locations, and 
interior locations subject to moderate degrees of moisture, such as some 
basements, some barns, and some cold-storage warehouses.
    (ii) Dry location. A location not normally subject to dampness or 
wetness. A location classified as dry may be temporarily subject to 
dampness or wetness, as in the case of a building under construction.
    (iii) Wet location. Installations underground or in concrete slabs 
or masonry in direct contact with the earth, and locations subject to 
saturation with water or other liquids, such as vehicle-washing areas, 
and locations exposed to weather and unprotected.
    May. If a discretionary right, privilege, or power is conferred, the 
word ``may'' is used. If a right, privilege, or power is abridged or if 
an obligation to abstain from acting is imposed, the word ``may'' is 
used with a restrictive ``no,'' ``not,'' or ``only.'' (E.g., no employer 
may . . . ; an employer may not . . . ; only qualified persons may. . . 
    Medium voltage cable. Type MV medium voltage cable is a single or 
multiconductor solid dielectric insulated cable rated 2000 volts or 
    Metal-clad cable. Type MC cable is a factory assembly of one or more 
conductors, each individually insulated and enclosed in a metallic 
sheath of interlocking tape, or a smooth or corrugated tube.
    Mineral-insulated metal-sheathed cable. Type MI mineral-insulated 
metal-sheathed cable is a factory assembly of one or more conductors 
insulated with a highly compressed refractory mineral insulation and 
enclosed in a liquidtight and gastight continuous copper sheath.
    Mobile X-ray. X-ray equipment mounted on a permanent base with 
wheels and/or casters for moving while completely assembled.
    Nonmetallic-sheathed cable. Nonmetallic-sheathed cable is a factory 
assembly of two or more insulated conductors having an outer sheath of 
moisture resistant, flame-retardant, nonmetallic material. Nonmetallic 
sheathed cable is manufactured in the following types:
    (i) Type NM. The overall covering has a flame-retardant and 
moisture-resistant finish.
    (ii) Type NMC. The overall covering is flame-retardant, moisture-
resistant, fungus-resistant, and corrosion-resistant.
    Oil (filled) cutout. (Over 600 volts, nominal.) A cutout in which 
all or part of the fuse support and its fuse link or disconnecting blade 
are mounted in oil with complete immersion of the contacts and the 
fusible portion of the conducting element (fuse link), so that arc 
interruption by severing of the fuse link or by opening of the contacts 
will occur under oil.

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    Open wiring on insulators. Open wiring on insulators is an exposed 
wiring method using cleats, knobs, tubes, and flexible tubing for the 
protection and support of single insulated conductors run in or on 
buildings, and not concealed by the building structure.
    Outlet. A point on the wiring system at which current is taken to 
supply utilization equipment.
    Outline lighting. An arrangement of incandescent lamps or electric 
discharge tubing to outline or call attention to certain features such 
as the shape of a building or the decoration of a window.
    Oven, wall-mounted. An oven for cooking purposes designed for 
mounting in or on a wall or other surface and consisting of one of more 
heating elements, internal wiring, and built-in or separately mountable 
controls. (See Cooking unit, counter-mounted.)
    Overcurrent. Any current in excess of the rated current of equipment 
or the ampacity of a conductor. It may result from overload (see 
definition), short circuit, or ground fault. A current in excess of 
rating may be accommodated by certain equipment and conductors for a 
given set of conditions. Hence the rules for overcurrent protection are 
specific for particular situations.
    Overload. Operation of equipment in excess of normal, full load 
rating, or of a conductor in excess of rated ampacity which, when it 
persists for a sufficient length of time, would cause damage or 
dangerous overheating. A fault, such as a short circuit or ground fault, 
is not an overload. (See Overcurrent.)
    Panelboard. A single panel or group of panel units designed for 
assembly in the form of a single panel; including buses, automatic 
overcurrent devices, and with or without switches for the control of 
light, heat, or power circuits; designed to be placed in a cabinet or 
cutout box placed in or against a wall or partition and accessible only 
from the front. (See Switchboard.)
    Permanently installed decorative fountains and reflection pools. 
Those that are constructed in the ground, on the ground, or in a 
building in such a manner that the pool cannot be readily disassembled 
for storage and are served by electrical circuits of any nature. These 
units are primarily constructed for their aesthetic value and not 
intended for swimming or wading.
    Permanently installed swimming pools, wading and therapeutic pools. 
Those that are constructed in the ground, on the ground, or in a 
building in such a manner that the pool cannot be readily disassembled 
for storage whether or not served by electrical circuits of any nature.
    Portable X-ray. X-ray equipment designed to be hand-carried.
    Power and control tray cable. Type TC power and control tray cable 
is a factory assembly of two or more insulated conductors, with or 
without associated bare or covered grounding conductors under a 
nonmetallic sheath, approved for installation in cable trays, in 
raceways, or where supported by a messenger wire.
    Power fuse. (Over 600 volts, nominal.) See Fuse.
    Power-limited tray cable. Type PLTC nonmetallic-sheathed power 
limited tray cable is a factory assembly of two or more insulated 
conductors under a nonmetallic jacket.
    Power outlet. An enclosed assembly which may include receptacles, 
circuit breakers, fuseholders, fused switches, buses and watt-hour meter 
mounting means; intended to supply and control power to mobile homes, 
recreational vehicles or boats, or to serve as a means for distributing 
power required to operate mobile or temporarily installed equipment.
    Premises wiring system. That interior and exterior wiring, including 
power, lighting, control, and signal circuit wiring together with all of 
its associated hardware, fittings, and wiring devices, both permanently 
and temporarily installed, which extends from the load end of the 
service drop, or load end of the service lateral conductors to the 
outlet(s). Such wiring does not include wiring internal to appliances, 
fixtures, motors, controllers, motor control centers, and similar 
    Qualified person. One familiar with the construction and operation 
of the equipment and the hazards involved.

    Note 1: Whether an employee is considered to be a ``qualified 
person'' will depend upon various circumstances in the workplace. It is 
possible and, in fact, likely for an individual

[[Page 875]]

to be considered ``qualified'' with regard to certain equipment in the 
workplace, but ``unqualified'' as to other equipment. (See 
Sec. 1910.332(b)(3) for training requirements that specifically apply to 
qualified persons.)
    Note 2: An employee who is undergoing on-the-job training and who, 
in the course of such training, has demonstrated an ability to perform 
duties safely at his or her level of training and who is under the 
direct supervision of a qualified person is considered to be a qualified 
person for the performance of those duties.

    Raceway. A channel designed expressly for holding wires, cables, or 
busbars, with additional functions as permitted in this subpart. 
Raceways may be of metal or insulating material, and the term includes 
rigid metal conduit, rigid nonmetallic conduit, intermediate metal 
conduit, liquidtight flexible metal conduit, flexible metallic tubing, 
flexible metal conduit, electrical metallic tubing, underfloor raceways, 
cellular concrete floor raceways, cellular metal floor raceways, surface 
raceways, wireways, and busways.
    Readily accessible. Capable of being reached quickly for operation, 
renewal, or inspections, without requiring those to whom ready access is 
requisite to climb over or remove obstacles or to resort to portable 
ladders, chairs, etc. (See Accessible.)
    Receptacle. A receptacle is a contact device installed at the outlet 
for the connection of a single attachment plug. A single receptacle is a 
single contact device with no other contact device on the same yoke. A 
multiple receptacle is a single device containing two or more 
    Receptacle outlet. An outlet where one or more receptacles are 
    Remote-control circuit. Any electric circuit that controls any other 
circuit through a relay or an equivalent device.
    Sealable equipment. Equipment enclosed in a case or cabinet that is 
provided with a means of sealing or locking so that live parts cannot be 
made accessible without opening the enclosure. The equipment may or may 
not be operable without opening the enclosure.
    Separately derived system. A premises wiring system whose power is 
derived from generator, transformer, or converter winding and has no 
direct electrical connection, including a solidly connected grounded 
circuit conductor, to supply conductors originating in another system.
    Service. The conductors and equipment for delivering energy from the 
electricity supply system to the wiring system of the premises served.
    Service cable. Service conductors made up in the form of a cable.
    Service conductors. The supply conductors that extend from the 
street main or from transformers to the service equipment of the 
premises supplied.
    Service drop. The overhead service conductors from the last pole or 
other aerial support to and including the splices, if any, connecting to 
the service-entrance conductors at the building or other structure.
    Service-entrance cable. Service-entrance cable is a single conductor 
or multiconductor assembly provided with or without an overall covering, 
primarily used for services and of the following types:
    (i) Type SE, having a flame-retardant, moisture-resistant covering, 
but not required to have inherent protection against mechanical abuse.
    (ii) Type USE, recognized for underground use, having a moisture-
resistant covering, but not required to have a flame-retardant covering 
or inherent protection against mechanical abuse. Single-conductor cables 
having an insulation specifically approved for the purpose do not 
require an outer covering.
    Service-entrance conductors, overhead system. The service conductors 
between the terminals of the service equipment and a point usually 
outside the building, clear of building walls, where joined by tap or 
splice to the service drop.
    Service entrance conductors, underground system. The service 
conductors between the terminals of the service equipment and the point 
of connection to the service lateral. Where service equipment is located 
outside the building walls, there may be no service-entrance conductors, 
or they may be entirely outside the building.
    Service equipment. The necessary equipment, usually consisting of a 
circuit breaker or switch and fuses, and their accessories, located near 

[[Page 876]]

point of entrance of supply conductors to a building or other structure, 
or an otherwise defined area, and intended to consititute the main 
control and means of cutoff of the supply.
    Service raceway. The raceway that encloses the service-entrance 
    Shielded nonmetallic-sheathed cable. Type SNM, shielded nonmetallic-
sheathed cable is a factory assembly of two or more insulated conductors 
in an extruded core of moisture-resistant, flame-resistant nonmetallic 
material, covered with an overlapping spiral metal tape and wire shield 
and jacketed with an extruded moisture-, flame-, oil-, corrosion-, 
fungus-, and sunlight-resistant nonmetallic material.
    Show window. Any window used or designed to be used for the display 
of goods or advertising material, whether it is fully or partly enclosed 
or entirely open at the rear and whether or not it has a platform raised 
higher than the street floor level.
    Sign. See Electric sign.
    Signaling circuit. Any electric circuit that energizes signaling 
    Special permission. The written consent of the authority having 
    Storable swimming or wading pool. A pool with a maximum dimension of 
15 feet and a maximum wall height of 3 feet and is so constructed that 
it may be readily disassembled for storage and reassembled to its 
original integrity.
    Switchboard. A large single panel, frame, or assembly of panels 
which have switches, buses, instruments, overcurrent and other 
protective devices mounted on the face or back or both. Switchboards are 
generally accessible from the rear as well as from the front and are not 
intended to be installed in cabinets. (See Panelboard.)
    (i) General-use switch. A switch intended for use in general 
distribution and branch circuits. It is rated in amperes, and it is 
capable of interrupting its rated current at its rated voltage.
    (ii) General-use snap switch. A form of general-use switch so 
constructed that it can be installed in flush device boxes or on outlet 
box covers, or otherwise used in conjunction with wiring systems 
recognized by this subpart.
    (iii) Isolating switch. A switch intended for isolating an electric 
circuit from the source of power. It has no interrupting rating, and it 
is intended to be operated only after the circuit has been opened by 
some other means.
    (iv) Motor-circuit switch. A switch, rated in horsepower, capable of 
interrupting the maximum operating overload current of a motor of the 
same horsepower rating as the switch at the rated voltage.
    Switching devices. (Over 600 volts, nominal.) Devices designed to 
close and/or open one or more electric circuits. Included in this 
category are circuit breakers, cutouts, disconnecting (or isolating) 
switches, disconnecting means, interrupter switches, and oil (filled) 
    Transportable X-ray. X-ray equipment installed in a vehicle or that 
may readily be disassembled for transport in a vehicle.
    Utilization equipment. Utilization equipment means equipment which 
utilizes electric energy for mechanical, chemical, heating, lighting, or 
similar useful purpose.
    Utilization system. A utilization system is a system which provides 
electric power and light for employee workplaces, and includes the 
premises wiring system and utilization equipment.
    Ventilated. Provided with a means to permit circulation of air 
sufficient to remove an excess of heat, fumes, or vapors.
    Volatile flammable liquid. A flammable liquid having a flash point 
below 38 degrees C (100 degrees F) or whose temperature is above its 
flash point.
    Voltage (of a circuit). The greatest root-mean-square (effective) 
difference of potential between any two conductors of the circuit 
    Voltage, nominal. A nominal value assigned to a circuit or system 
for the purpose of conveniently designating its voltage class (as 120/
240, 480Y/277, 600, etc.). The actual voltage at which a circuit 
operates can vary from the nominal within a range that permits 
satisfactory operation of equipment.
    Voltage to ground. For grounded circuits, the voltage between the 
given conductor and that point or conductor of the circuit that is 
grounded; for

[[Page 877]]

ungrounded circuits, the greatest voltage between the given conductor 
and any other conductor of the circuit.
    Watertight. So constructed that moisture will not enter the 
    Weatherproof. So constructed or protected that exposure to the 
weather will not interfere with successful operation. Rainproof, 
raintight, or watertight equipment can fulfill the requirements for 
weatherproof where varying weather conditions other than wetness, such 
as snow, ice, dust, or temperature extremes, are not a factor.
    Wet location. See Location.
    Wireways. Wireways are sheet-metal troughs with hinged or removable 
covers for housing and protecting electric wires and cable and in which 
conductors are laid in place after the wireway has been installed as a 
complete system.

[46 FR 4056, Jan. 16, 1981; 46 FR 40185, Aug. 7, 1981, as amended at 53 
FR 12123, Apr. 12, 1988; 55 FR 32020, Aug. 6, 1990; 55 FR 46054, Nov. 1, 

        Appendix A to Subpart S of Part 1910--Reference Documents

    The following references provide information which can be helpful in 
understanding and complying with the requirements contained in Subpart 
ANSI A17.1-71  Safety Code for Elevators, Dumbwaiters, Escalators and 
          Moving Walks.
ANSI B9.1-71  Safety Code for Mechanical Refrigeration.
ANSI B30.2-76  Safety Code for Overhead and Gantry Cranes.
ANSI B30.3-75  Hammerhead Tower Cranes.
ANSI B30.4-73  Safety Code for Portal, Tower, and Pillar Cranes.
ANSI B30.5-68  Safety Code for Crawler, Locomotive, and Truck Cranes.
ANSI B30.6-77  Derricks.
ANSI B30.7-77  Base Mounted Drum Hoists.
ANSI B30.8-71  Safety Code for Floating Cranes and Floating Derricks.
ANSI B30.11-73  Monorail Systems and Underhung Cranes.
ANSI B30.12-75  Handling Loads Suspended from Rotorcraft.
ANSI B30.13-77  Controlled Mechanical Storage Cranes.
ANSI B30.15-73  Safety Code for Mobile Hydraulic Cranes.
ANSI B30.16-73  Overhead Hoists.
ANSI C2-81  National Electrical Safety Code.
ANSI C33.27-74  Safety Standard for Outlet Boxes and Fittings for Use in 
          Hazardous Locations, Class I, Groups A, B, C, and D, and Class 
          II, Groups E, F, and G.
ANSI K61.1-72  Safety Requirements for the Storage and Handling of 
          Anhydrous Ammonia.
ASTM D2155-66  Test Method for Autoignition Temperature of Liquid 
          Petroleum Products.
ASTM D3176-74  Method for Ultimate Analysis of Coal and Coke.
ASTM D3180-74  Method for Calculating Coal and Coke Analyses from As 
          Determined to Different Bases.
IEEE 463-77  Standard for Electrical Safety Practices in Electrolytic 
          Cell Line Working Zones.
NFPA 20-76  Standard for the Installation of Centrifugal Fire Pumps.
NFPA 30-78  Flammable and Combustible Liquids Code.
NFPA 32-74  Standard for Drycleaning Plants.
NFPA 33-73  Standard for Spray Application Using Flammable and 
          Combustible Materials.
NFPA 34-74  Standard for Dip Tanks Containing Flammable or Combustible 
NFPA 35-76  Standard for the Manufacture of Organic Coatings.
NFPA 36-74  Standard for Solvent Extraction Plants.
NFPA 40-74  Standard for the Storage and Handling of Cellulose Nitrate 
          Motion Picture Film.
NFPA 56A-73  Standard for the Use of Inhalation Anesthetics (Flammable 
          and Nonflammable).
NFPA 56F-74  Standard for Nonflammable Medical Gas Systems.
NFPA 58-76  Standard for the Storage and Handling of Liquefied Petroleum 
NFPA 59-76  Standard for the Storage and Handling of Liquefied Petroleum 
          Gases at Utility Gas Plants.
NFPA 70-78  National Electrical Code.
NFPA 70C-74  Hazardous Locations Classification.
NFPA 70E  Standard for the Electrical Safety Requirements for Employee 
NFPA 71-77  Standard for the Installation, Maintenance, and Use of 
          Central Station Signaling Systems.
NFPA 72A-75  Standard for the Installation, Maintenance, and Use of 
          Local Protective Signaling Systems for Watchman, Fire Alarm, 
          and Supervisory Service.
NFPA 72B-75  Standard for the Installation, Maintenance, and Use of 
          Auxiliary Protective Signaling Systems for Fire Alarm Service.
NFPA 72C-75  Standard for the Installation, Maintenance, and Use of 
          Remote Station Protective Signaling Systems.
NFPA 72D-75  Standard for the Installation, Maintenance, and Use of 

[[Page 878]]

          Protective Signaling Systems for Watchman, Fire Alarm, and 
          Supervisory Service.
NFPA 72E-74  Standard for Automatic Fire Detectors.
NFPA 74-75  Standard for Installation, Maintenance, and Use of Household 
          Fire Warning Equipment.
NFPA 76A-73  Standard for Essential Electrical Systems for Health Care 
NFPA 77-72  Recommended Practice on Static Electricity.
NFPA 80-77  Standard for Fire Doors and Windows.
NFPA 86A-73  Standard for Ovens and Furnaces; Design, Location and 
NFPA 88A-73  Standard for Parking Structures.
NFPA 88B-73  Standard for Repair Garages.
NFPA 91-73  Standard for the Installation of Blower and Exhaust Systems 
          for Dust, Stock, and Vapor Removal, or Conveying.
NFPA 101-78  Code for Safety to Life from Fire in Buildings and 
          Structures. (Life Safety Code.)
NFPA 325M-69  Fire-Hazard Properties of Flammable Liquids, Gases, and 
          Volatile Solids.
NFPA 493-75  Standard for Intrinsically Safe Apparatus for Use in Class 
          I Hazardous Locations and Its Associated Apparatus.
NFPA 496-74  Standard for Purged and Pressurized Enclosures for 
          Electrical Equipment in Hazardous Locations.
NFPA 497-75  Recommended Practice for Classification of Class I 
          Hazardous Locations for Electrical Installations in Chemical 
NFPA 505-75  Fire Safety Standard for Powered Industrial Trucks 
          Including Type Designations and Areas of Use.
NMAB 353-1-79  Matrix of Combustion-Relevant Properties and 
          Classification of Gases, Vapors, and Selected Solids.
NMAB 353-2-79  Test Equipment for Use in Determining Classifications of 
          Combustible Dusts.
NMAB 353-3-80  Classification of Combustible Dusts in Accordance with 
          the National Electrical Code.

[46 FR 4056, Jan. 16, 1981; 46 FR 40185, Aug. 7, 1981]

    Appendix B to Subpart S to Part 1910--Explanatory Data [Reserved]

    Appendix C to Subpart S to Part 1910--Tables, Notes, and Charts