**Table of contents**

[12 Personnel safety 12-1](#personnel-safety)

[12.1 General 12-1](#general)

[12.2 Work space safety 12-1](#work-space-safety)

[12.2.1 General 12-1](#general-1)

[12.2.2 Platforms, ramps, stairs, ladders, and handholds
12-4](#platforms-ramps-stairs-ladders-and-handholds)

[12.3 Equipment-related safety 12-6](#equipment-related-safety)

[12.4 Electrical hazards 12-7](#electrical-hazards)

[12.4.1 General 12-8](#general-2)

[12.4.2 Switches 12-11](#switches)

[12.4.3 Discharging devices 12-12](#discharging-devices)

[12.4.4 Grounding 12-13](#grounding)

[12.4.5 Electrical tools and self-powered equipment
12-15](#electrical-tools-and-self-powered-equipment)

[12.5 Physical hazards 12-16](#physical-hazards)

[12.5.1 General 12-16](#general-3)

[12.5.2 Guards, caps, and shields 12-19](#guards-caps-and-shields)

[12.6 Liquid and gas hazards 12-20](#liquid-and-gas-hazards)

[12.7 Toxic hazards 12-20](#toxic-hazards)

[12.8 Radiation hazards 12-22](#radiation-hazards)

[12.9 Protection from special chemicals
12-23](#protection-from-special-chemicals)

[12.10 Temperature hazards 12-24](#temperature-hazards)

[12.11 Fire Protection 12-25](#fire-protection)

[12.12 Noise hazards 12-26](#noise-hazards)

[12.13 Explosion and implosion hazards
12-29](#explosion-and-implosion-hazards)

[12.14 Radiant energy hazards 12-30](#radiant-energy-hazards)

[12.14.1 Ultraviolet radiant energy (200-315 nm)
12-30](#ultraviolet-radiant-energy-200-315-nm)

[12.14.2 Near-ultraviolet radiant energy (315-400 nm)
12-31](#near-ultraviolet-radiant-energy-315-400-nm)

[12.14.3 Visible and near-infrared radiant energy (400-1400 nm)
12-31](#visible-and-near-infrared-radiant-energy-400-1400-nm)

[12.14.4 Far-infrared radiant energy (1400-10^6^ nm)
12-34](#far-infrared-radiant-energy-1400-106-nm)

[12.14.5 Microwave radiant energy (10^7^-10^11^ Hz)
12-34](#microwave-radiant-energy-107-1011-hz)

[12.15 Laser hazards 12-34](#laser-hazards)

[12.16 Safety labels and placards 12-35](#safety-labels-and-placards)

[Glossary 12-39](#__RefHeading___Toc26951006)

[References 12-40](#__RefHeading___Toc26951007)

[Index 12-42](#__RefHeading___Toc26951008)

**List of exhibits**

[**Exhibit 12.2.1.8 Specific task illumination requirements
12-4**](#__RefHeading___Toc26685375)

[Exhibit 12.4 Shock current intensities and their effects
12-7](#__RefHeading___Toc26685376)

[Exhibit 12.4.1.3 Proof test values for protective gloves
12-9](#__RefHeading___Toc26685377)

[Exhibit 12.4.1.9 An interlock switch
12-10](#__RefHeading___Toc26685378)

[Exhibit 12.4.3.3 Automatic shorting bar
12-13](#__RefHeading___Toc26685379)

[Exhibit 12.4.4.6 Equipment grounding
12-14](#__RefHeading___Toc26685380)

[Exhibit 12.5.1.4 (a) Rolling edges of sheets less than 0.5 mm (0.02 in)
thick. 12-17](#__RefHeading___Toc26685381)

[Exhibit 12.5.1.4 (b) Rounding exposed edges 0.5 up to 3.0 mm (0.02 up
to 0.12 in) thick. 12-17](#__RefHeading___Toc26685382)

[Exhibit 12.5.1.4 (c) Rounding exposed edges 3.0 to 6.4 mm (0.12 up to
0.25 in) thick. 12-17](#__RefHeading___Toc26685383)

[Exhibit 12.5.1.4 (d) Rounding of exposed edges 6.4 mm (0.25 in) thick
or greater 12-17](#__RefHeading___Toc26685384)

[Exhibit 12.5.1.5 (a) Requirements for rounding of corners less than 25
mm (1.0 in) thick 12-18](#__RefHeading___Toc26685385)

[Exhibit 12.5.1.5 (b) Requirements for rounding of corners greater than
25 mm (1.0 in) thick ...12-18](#__RefHeading___Toc26685385)

[Exhibit 12.10.1 Upper and lower temperature limit range
12-24](#__RefHeading___Toc26685387)

[Exhibit 12.12.8 Permissible noise exposure.
12-28](#__RefHeading___Toc26685388)

[Exhibit 12.14.1.1 Exposure limit for ultraviolet radiant energy (200 to
315 mm) 12-30](#__RefHeading___Toc26685389)

[Exhibit 12.14.3 Relative contribution of different wavelengths to
luminance --the luminosity function 12-32](#__RefHeading___Toc26685390)

[Exhibit 12.14.3.1 Maximum safe exposure to 400-1400 nm radiant energy.
12-32](#__RefHeading___Toc26685391)

[Exhibit 12.14.3.4 Estimation of permissible image luminance
12-33](#__RefHeading___Toc26685392)

[Exhibit 12.16.2 Label and placard layout --two panel sign with optional
symbol panel 12-36](#__RefHeading___Toc26685393)

#  Personnel safety

Human factors design rules that enhance the safety of FAA maintenance
personnel are discussed in this section. Chapter 4, Designing equipment
for maintenance; Chapter 10, Workplace design; and Chapter 13,
Environment, also contain safety rules specific to their respective
domains.

## 12.1 General

This general section discusses safety factors that are derived from
human engineering and from application of military safety considerations
and from FAA and OSHA health and safety considerations. The latter have
precedence.

-   **12.1.1** **Safety factors.** As part of facility and equipment
    design, safety factors shall be given major consideration,
    including, as a minimum, the representative safety rules herein,
    together with the effective application of the human engineering
    rules in other sections of this document. Safety factors are also
    determined from the application of MIL-STD-822B to the acquisition
    program and from FAA Order 3900.19(B), OSHA 29 CFR 1910 and 1926 as
    they apply to the program. In the area of safety and health OSHA and
    FAA documents have precedence. \[Source: 29 CFR 1910 and 1926;
    Department of Defense (MIL-STD-1472F), 1999\]

## 12.2 Work space safety

Rules addressing general work space safety including the safety of
maintainers using platforms, ramps, stairs, ladders, and handholds are
given in this section.

### 12.2.1 General

-   **12.2.1.1 Hazard alerting or alarm devices.** A hazard alerting or
    alarm device shall be provided to warn personnel of impending danger
    or existing hazards such as fire, radio frequency or X radiation, or
    the presence of combustible or asphyxiating gas. OSHA 29 CFR
    1910.165 shall govern employee alarms for fire or other hazards that
    require escape (see also OSHA 29 CFR 1910.165 Appendixes A, B, and C
    for rules). \[Source: 29 CFR 1910.165; MIL-STD-1472F, 1999;
    Department of Energy (DOE-HFAC1), 1992\]

-   **12.2.1.2 Location.** Hazard alerting or alarm devices shall be
    located where the people who must take corrective action can easily
    distinguish them. \[Source: MIL-STD-1472F, 1999; DOE-HFAC1, 1992\]

-   **12.2.1.3** **Redundant hazard alerting or alarm devices.**
    Redundant hazard-alerting devices of different types, for example, a
    light and a bell, shall be required if ambient noise could mask the
    audible alarm, or if the warning light could not be seen in the
    ambient illumination. Tactile devices may be used to alert employees
    who would not otherwise be able to recognize audible or visual
    alarms. \[Source: MIL-STD-1472F, 1999; DOE-HFAC1, 1992\]

-   **12.2.1.4** **Physical barriers.** Physical barriers (for example,
    safety chains, guards, shields, or walls) shall be provided in
    addition to safety labels, placards, and signs, to prevent contact
    with hazards, such as moving parts of machinery. Fixed and portable
    power tools shall be guarded in accordance with OSHA 29 CFR 1910.212
    -247. Live electrical parts operating at 50 or more volts shall be
    guarded in accordance with OSHA 29 CFR 1910.303 (b)(2). Floor and
    wall openings shall be guarded in accordance with 29 CFR 1910.23.
    Power transmission apparatus shall be guarded in accordance with
    OSHA 29 CFR 1910.219. \[Source: CFR 1910.212 --247, 29 CFR 1910.303;
    Department of Defense (MIL-HDBK-759B), 1992\]

-   **12.2.1.5** **Obstruction-free.** Work spaces shall be free of
    obstructions that could cause injury to personnel either through
    accidental contact with the obstruction or because the obstruction
    forces the maintainer to adopt an awkward position. In accordance
    with OSHA 29 CFR 1910.22, all workplaces shall be kept clean and dry
    and shall not have obstructions where they would cause a hazard.
    \[Source: 29 CFR 1910.22, MIL-STD-1472F, 1999; DOE-HFAC1, 1992\]

-   **12.2.1.6** **Emergency door and exit design and construction.**
    Emergency doors and exits shall be designed and constructed so that
    they:

a.  are simple to operate,

b.  are readily accessible,

c.  are clearly designated,

d.  are unobstructed,

e.  are simple to locate and operate in the dark,

f.  are capable of being opened in 3 sec or less,

g.  require 44 to 133 N (10 to 30 lb) of operating force to open,

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h.  permit exit by one person in 5 sec or less, and

i.  do not in themselves, or in their operation, constitute a safety
    hazard. \[Source: MIL-STD-1472F, 1999; DOE-HFAC1, 1992\]

**Note.** Means of egress and exit shall comply with OSHA 29 CFR 1910.35
-40.

-   **12.2.1.7** **Nonskid surfaces.** Stairs, ramps, platforms, and
    catwalks shall have skid-proof flooring, stair, and step treads.
    Where applicable, surfaces shall be treated with nonskid material
    that conforms to MIL-W-5044 and that is applied in accordance with
    MIL-W-5050. \[Source: MIL-STD-1472F, 1999; DOE-HFAC1, 1992\]

-   **12.2.1.8** **Illumination.** Adequate illumination shall be
    provided for all work spaces. Recommended and minimum levels are
    given in Exhibit 12.2.1.8. \[Source: MIL-STD-1472F, 1999; DOE-HFAC1,
    1992\]

> []{#__RefHeading___Toc26685375 .anchor}**Exhibit 12.2.1.8** Specific
> task illumination requirements

### 12.2.2 Platforms, ramps, stairs, ladders, and handholds

-   **12.2.2.1** **Self-locking devices.** Self-locking or other
    fail-safe devices shall be incorporated on elevating stands, work
    platforms, and \"draw bridges\" to prevent accidental or inadvertent
    collapsing or falling. Safety requirements of OSHA 29 CFR 1910.21
    -30 shall also apply to platforms and scaffolding. \[Source: 29 CFR
    1910.21 --30; MIL-STD-1472F, 1999; MIL-HDBK-759B, 1992\]

-   **12.2.2.2** **High centers of gravity.** Platforms that have a high
    center of gravity shall have anchors or outriggers for stability.
    \[Source: MIL-HDBK-759B, 1992\]

-   **12.2.2.3** **Safety measures.** Guardrails, safety bars, or chains
    shall be installed around platforms and across stair or step
    openings of ledges, catwalks, and the like. These guards shall be
    1.1 m (42 in) above the standing surface. An additional guardrail
    shall also be provided between the platform and the top guardrail,
    safety bar, or chain. These top guardrails shall be no more than 1.1
    m (42 in.) and no less than 91 cm (36 in.) from the platform. Safety
    chains shall only be used where it is not feasible to install
    guardrail or safety bars. \[Source: MIL-STD-1472F, 1999\]

-   **12.2.2.4** **Toe board or guard screen.** A toe board of 10 cm (4
    in) to 15 cm (4 in) shall be used to guard floor openings or a guard
    screen shall extend from the floor base to the intermediate rail.
    \[Source: MIL-STD-1472F, 1999\]

    **Note.** OSHA 29 CFR 1910.23 (e) permits a 102 mm (4 in) toe board
    as a minimum.

    **Discussion.** The guard screen is used to prevent a person who
    falls on the platform from falling from the platform. It can also
    prevent most tools, parts, and equipment from falling from the
    platform. Toe boards are intended to prevent tools, parts, and
    equipment from falling as well as to prevent the worker\'s foot from
    slipping off the edge of the platform.

-   **12.2.2.5** **Safety mesh.** Screen or safety mesh shall be
    installed on the underside of open gratings, platforms, or flooring
    surfaces where there is a possibility that small tools, parts, or
    debris may fall through the grating onto maintainers or equipment
    beneath the platform. \[Source: MIL-STD-1472F, 1999\]

-   **12.2.2.6** **Telescoping ladders.** Adequate finger clearance
    shall be provided between the moving parts of telescoping ladders.
    \[Source: MIL-STD-1472F, 1999\]

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-   **12.2.2.7** **De-icing ladders and steps.** Ladders and steps
    should be designed so they can be de-iced with hot water or steam.
    \[Source: MIL-HDBK-759B, 1992\]

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-   **12.2.2.8** **Handholds.** Handholds shall be furnished where
    needed to assist maintainers in climbing onto a platform or in
    performing the intended maintenance tasks from the platform.
    \[Source: MIL-STD-1472F, 1999\]

-   **12.2.2.9** **Nonfixed handholds.** When a flat surface is desired,
    handholds shall fold or telescope so they are concealed or flush
    with the surface except when they are being used. Folding hand grips
    shall remain securely folded when not in use and maintainers shall
    not need tools to open them. \[Source: MIL-HDBK-759B, 1992\]

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-   **12.2.2.10** **Fixed handholds.** Handholds should be fixed except
    when a flat surface is desired. \[Source: MIL-HDBK-759B, 1992\]

## 12.3 Equipment-related safety

Safety factors need to be a major part of equipment design. This section
gives rules to protect from possible injury when using or working with
hazardous equipment.

-   **12.3.1** **Hazardous operations.** The operation of switches or
    controls that initiate hazardous operations (for example,
    equipment-moving devices) shall require the prior operation of a
    related or locking control. When practical, the critical position of
    such a control shall activate a visual and auditory warning device
    in the affected work area. \[Source: MIL-STD-1472F, 1999; DOE-HFAC1,
    1992\]

-   **12.3.2** **Accessibility.** Units of equipment shall be located
    and mounted so that they are accessible to the maintainer with
    minimal danger from electrical charge, heat, moving parts,
    radiation, or other hazards (see also Paragraph 12.4.1.1). \[Source:
    MIL-STD-1472F, 1999; DOE-HFAC1, 1992\]

-   **12.3.3** **Test equipment stability.** Equipment, particularly
    portable equipment such as maintenance stands, tables, benches,
    platforms, and ladders, shall be designed for maximum stability and
    shall meet OSHA requirements. \[Source: MIL-HDBK-759B, 1992\]

-   **12.3.4** **Equipment with wheels.** Equipment with wheels shall be
    designed to maximize stability and safety when it is moved on ramps
    or inclines. \[Source: MIL-HDBK-759B, 1992\]

    **Discussion.** Ramps and inclines change the equipment\'s center of
    gravity. The lower wheels bear a majority of the weight. With
    heavier equipment, this may mean that weight is concentrated enough
    to exceed allowable ramp loads. Shifting the center of gravity also
    increases the risk that equipment will overturn.

-   **12.3.5** **Mechanically stored energy devices.** Personnel shall
    be protected from mechanical devices capable of storing energy, such
    as springs, levers, and torsion bars. A means shall be provided to
    release the stored energy. \[Source: National Aeronautics and Space
    Administration (NASA-STD-3000A), 1989\]

    **Discussion.** Protection can be achieved by shielding the stored
    energy devices. The release of stored energy can be achieved by a
    device that automatically releases the energy or by a device or
    procedure that permits the personnel to safely release the energy.

-   **12.3.6** **Safety features.** Where stored energy devices are
    necessary, safety features such as removal tabs, lockouts, and
    warning placards shall be provided (see also Section 12.16).
    \[Source: NASA-STD-3000A, 1989\]

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-   **12.3.7** **Equipment coloring.** Equipment designed for safety,
    protective, or emergency functions should be colored in accordance
    with MIL-STD-1473. \[Source: MIL-HDBK-759B, 1992\]

## 12.4 Electrical hazards

The principal electrical hazard is shock. The effects of electric shock
depend on the body\'s resistance, the current path through the body, the
duration of the shock, the amount of current and voltage, the frequency
of the alternating current, and the individual\'s physical condition.
The most critical determinant of injuries is the amount of current
conducted through the body. Besides the obvious risk of burns and
injuries to the nervous system, electric shock can produce involuntary
muscular reactions that injure people. Exhibit 12.4 gives the typical
effects of various current intensities. All electrical systems of 30
volts or more are potential shock hazards. Research reveals that most
shock deaths result from contacts with electrical systems ranging from
70 to 500 volts. Under extraordinary circumstances, even voltages below
30 volts can cause injury. \[Source: MIL-HDBK-759B, 1992;NASA-STD-3000A,
1989\]

> []{#__RefHeading___Toc26685376 .anchor}**Exhibit 12.4** Shock current
> intensities and their effects

### 12.4.1 General {#general-2 .unnumbered}

The two basic types of safety switches for preventing electric shock are
interlocks and main-power switches. \[Source: MIL-HDBK-759B, 1992\]

**Definitions.** **Interlocks** are devices (for example, switches)
connected with a cover, shield, or case that disable the associated
internal hazard (usually electrical) when the cover, shield, or case is
opened. OSHA regulations discuss lockout and tagout procedures to be
used in the workplace during maintenance or operations to protect from
electrical hazards. A **lockout** uses a mechanical mean to disable a
control or switch in its safe position (for example, electricity
disconnected) and to prevent its activation without the use of undue
force or tools. **Tagouts** are tags that are attached to a control or
place of hazard associated with an ongoing mode of operation or
maintenance.

-   **12.4.1.1** **Protection from electric shock.** Personnel shall be
    protected from accidental contact with voltages in excess of 30
    volts AC or DC by interlocks, grounding, and other protective
    devices. \[Source: MIL-HDBK-759B, 1992; Department of Defense
    (MIL-STD-454M), 1989\]

    **Discussion.** Human protection from hazardous conditions with
    unexpected energy or release of stored energy is treated in OSHA 29
    CFR 1910.301 -308, 331 -335, and 399. OSHA 29 CFR 1910.333
    (b)(2)(iii)(A) requires the simultaneous use of both tagout and
    lockout in the workplace; OSHA 29 CFR 1910.333 (b)(2)(ii)(B) states
    that interlocks shall not be the sole mean of de-energizing circuits
    of equipment and are not substitutes for lockout and tagout
    procedures and practice. \[Source: 29 CFR 1910.301 -308, 331 -335,
    and 399\]

-   **12.4.1.2** **Rubber insulating equipment.** To help ensure the
    safety of personnel, insulated rubber gloves and live line tools
    shall be provided for personnel working on or near energized power
    circuits and equipment rated over 600 volts. \[Source: Department of
    Transportation (FAA Order 3900.19A), 1982\]

-   **12.4.1.3** **Selection of rubber insulating equipment.** Rubber
    protective equipment shall be selected in accordance with the
    voltages and equipment maintained. Exhibit 12.4.1.3 provides proof
    test for various classes of protective gloves. OSHA 29 CFR 1910.137
    specifies that the rubber protective equipment for electrical
    workers conform to ANSI standards. (See 29 CFR 1910.137 for testing
    of applicable ANSI standards). FAA Order 3900.19B 145B specifies
    that new rubber gloves shall be tested before used and at a minimum
    each 12 months. Reissued rubber glove shall be retested within 9
    months of issue. \[Source: 29 CFR 1910.137; FAA Order 3900.19A,
    1982\]

> []{#__RefHeading___Toc26685377 .anchor}**Exhibit 12.4.1.3** Proof test
> values for protective gloves

-   **12.4.1.4** **Static charge buildup.** Equipment design shall
    prevent static charge buildup or provide a method to discharge it.
    \[Source: NASA-STD-3000A, 1989\]

**Discussion.** The effects of electrostatic buildup can range from
minor discomfort (the shock from walking across a new carpet and
touching a metal object) to physical injury.

-   **12.4.1.5** **Fail-safe.** The design and development of all
    electronic equipment shall provide fail-safe features for safety of
    personnel during installation, operation, maintenance, and repair or
    interchanging of a complete equipment assembly or component parts.
    \[Source: 29 CFR 1910.7; MIL-STD-454M, 1989\]

-   **12.4.1.6** **Electrical conductors.** Electrical conductors with
    which personnel might come into contact during maintenance
    activities shall be insulated. \[Source: NASA-STD-3000A, 1989\]

-   **12.4.1.7** **Power.** Personnel shall be provided a means for
    removing power while they are installing, replacing, or repairing
    components or equipment. \[Source: MIL-STD-454M, 1989\]

-   **12.4.1.8** **Covers.** Grounded or nonconductive protective covers
    shall be provided for all electrical equipment. \[Source:
    NASA-STD-3000A, 1989\]

-   **12.4.1.9 Bypassable interlocks.** Doors, covers, or lids that
    provide access to voltage in the range of 70 to 500 volts shall have
    a bypassable interlock. Equipment that has been bypassed shall
    conform to OSHA 29 CFR 1910.333 (c)(10). Exhibit 12.4.1.9 shows an
    example of such an interlock. \[Source: 29 CFR 1910.333;
    MIL-HDBK-759B, 1992; NASA-STD-3000A, 1989; MIL-STD-454M, 1989\]

> []{#__RefHeading___Toc26685378 .anchor}**Exhibit 12.4.1.9** An
> interlock switch

![](media/image2.wmf){width="2.3979166666666667in"
height="2.316666666666667in"}

-   **12.4.1.10** **Non-bypassable interlocks.** Doors, covers or lids
    that provide access to voltages in excess of 500 volts or allow
    exposure to microwave and radio frequency radiation in excess of 300
    KHz shall have non-bypassable interlocks. \[Source: MIL-STD-454M,
    1989\]

-   **12.4.1.11** **Interlock override.** If a task requires that a
    maintainer work on hazardous equipment that is equipped with a
    disabling interlock, the equipment shall have an interlock override
    that permits manual bypassing or overriding of the interlock when
    the case or cover is open. This override shall automatically reset
    to the safety-protection position when the cover or case is
    replaced. OSHA 29 CFR 1910.333 requires that only qualified
    personnel shall be allowed to disable an interlock. \[Source: 29 CFR
    1910.333; Department of the Air Force (AFSC DH 1-3), 1980;
    Department of Energy (UCRL-15673), 1985; MIL-HDBK-759B, 1992\]

-   **12.4.1.12** **Medium voltage guarding.** If contacts, terminals,
    or other similar devices having voltages between 70 and 500 volts ac
    or dc with respect to ground are exposed, they shall be guarded from
    accidental contact by maintainers (see Paragraph 12.16.6 concerning
    wording for medium voltage labels and placards). \[Source:
    MIL-STD-454M, 1989\]

-   **12.4.1.13** **High voltage guarding.** Systems or equipment
    operating in excess of 500 volts ac or dc shall be completely
    enclosed (see Paragraph 12.16.7 concerning wording for high voltage
    labels and placards). \[Source: MIL-STD-454M, 1989\]

-   **12.4.1.14** **Guarding radio frequency (rf) voltages.**
    Transmitter output terminals, antennas, and other devices that carry
    sufficient rf voltage to burn or injure personnel shall be guarded
    from accidental contact. \[Source: MIL-STD-454M, 1989\]

-   **12.4.1.15** **Explosion-proof equipment.** All electrical
    equipment that will be used near flammable gases or vapors shall be
    explosion-proof. This equipment shall also be certified or listed by
    a nationally recognized testing laboratory recognized by OSHA (for
    example, Underwriters Laboratory). \[Source: MIL-HDBK-759B, 1992\]

-   **12.4.1.16** **Plugs and receptacles.** Plugs and receptacles shall
    be designed so that a plug of one voltage rating cannot be inserted
    into a receptacle of another rating. \[Source: MIL-STD-1472F, 1999;
    NASA-STD-3000A, 1989\]

-   **12.4.1.17** **\"Hot\" leads.** Wiring shall be routed through
    plugs and receptacles so that \"hot\" leads are not exposed in
    either the plug or the receptacle when they are disconnected.
    \[Source: MIL-STD-1472F, 1999; MIL-HDBK-759B, 1992\]

-   **12.4.1.18** **Design and location of electrical installations and
    electrical utilization equipment.** The design and location of
    electrical installations and electrical utilization equipment shall
    conform with OSHA 29 CFR 1910.302 through 308 which includes rules
    for workspace clearances around such equipment dependent upon its
    nominal voltage to ground and nominal voltage between phases for
    elevated energized parts. These rules apply to the protection of
    qualified electrical or electronic repair people, unqualified
    electrical or electronic repair people, and other unqualified
    personnel who could be exposed to electrical hazards or to
    electrical equipment in classified hazardous electrical locations.
    OSHA 29 CFR 1910.331 -335 address safety related work practices.
    \[Source: 29 CFR 1910.302\]

### 12.4.2 Switches

-   **12.4.2.1** **Main-power switches.** A unit of equipment shall have
    a clearly labeled main-power switch that turns off all power by
    opening leads from the main-power service connection. \[Source:
    MIL-HDBK-759B, 1992\]

-   **12.4.2.2** **Main-power switch location.** Main-power switches
    shall be located so that accidental contact by maintainers will not
    place the equipment in operation. A lockout shall be provided as
    specified in OSHA 29 CFR 1910.335 (b)(2). \[Source: 29
    CFR1910.333(b)(2); MIL-STD-454M, 1989\]

-   **12.4.2.3** **Physical protection at main-power switches.** The
    \"hot\" side of the main-power switch and the incoming power line
    connections shall be physically protected against accidental contact
    by maintainers. \[Source: MIL-STD-454M, 1989\]

-   **12.4.2.4** **Arc prevention.** Main-power switches shall be
    safeguarded to prevent heavy arcing. \[Source: MIL-HDBK-759B, 1992\]

-   **12.4.2.5** **Safety switches.** Safety switches that will
    deactivate associated mechanical drive components shall be provided
    for the purpose of disconnecting these components without
    disconnecting other parts of the equipment. \[Source: MIL-STD-454M,
    1989\]

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-   **12.4.2.6** **Switch box safety.** The switch box should be
    designed so the box cannot be opened when the switch is turned on.
    \[Source: MIL-HDBK-759B, 1992\]

### 12.4.3 Discharging devices

Circuits that contain capacitors can store lethal charges for relatively
long periods of time therefore all medium- and high- voltage power
supplies need devices that discharge the capacitors when they are turned
off.

-   **12.4.3.1** **Bleeders.** Bleeders shall be incorporated in all
    power supplies unless they can discharge 30 volts or less within 2
    sec after power removal. When a resistive bleeder network is used to
    discharge capacitors, the bleeder network shall consist of at least
    two equal valued resistors in parallel. \[Source: MIL-HDBK-759B,
    1992; MIL-STD-454M, 1989\]

    **Discussion.** It is better to discharge capacitors gradually,
    rather than shorting them. High-power resistors are often used in
    place of a grounding rod with several thousand ohms of resistance
    being a typical value. DC power supplies may be discharged when
    switched off by having a permanently connected bleeder resistor
    across the output terminals. The bleeder resistor needs to be of low
    enough resistance so that it is able to discharge the capacitors
    quickly after the power is turned off but not so low that it
    overloads the circuit.

-   **12.4.3.2** **Shorting rods.** Shorting rods shall be provided (in
    addition to bleeder resistors) with all equipment having voltages in
    excess of 70 volts ac or dc. \[Source: MIL-STD-454M, 1989\]

    **Discussion.** Some circuits with large, high-voltage capacitors
    (such as high-voltage radar equipment) cannot use bleeder resistors;
    other methods need to be used to discharge the capacitors before
    doing maintenance. Often capacitors are discharged with a shorting
    or grounding rod that has a well-insulated handle.

-   **12.4.3.3** **Removing power.** Interlocks shall remove power by
    mechanical releases or electrical solenoids, before automatic
    shorting bars (see Exhibit 12.4.3.3) discharge the power supply.
    These bars shall operate automatically whenever the enclosure is
    opened and function quickly, with high reliability. \[Source:
    MIL-HDBK-759B, 1992\]

> **Exhibit 12.4.3.3** Automatic shorting
> bar![](media/image3.png){width="4.459027777777778in"
> height="2.423611111111111in"}

-   **12.4.3.4** **Shorting rod storage.** Where size permits, shorting
    rods shall be stored within the transmitting equipment, permanently
    attached, and readily accessible to maintainers. The permanently
    attached rod shall be connected through a flexible stranded copper
    wire (covered with a transparent sleeve) to the stud provided at the
    transmitter main frame. Where size does not permit internal storage
    of a shorting rod, a grounding stud shall be provided to permit
    attachment of a portable shorting rod. The connection to the stud
    shall be such that accidental loosening or high resistance to the
    ground is prevented. \[Source: MIL-STD-454M, 1989\]

### 12.4.4 Grounding

Various grounding techniques are used to protect maintainers from
dangerous voltages in equipment. A terminal that is spot-welded to the
chassis provides a reliable ground connection. Rules for other methods
are also given in this section. \[Source: MIL-HDBK-759B, 1992\]

-   **12.4.4.1** **Same common ground.** All enclosures, exposed parts,
    and the chassis shall be kept at ground potential by a common
    ground. \[Source: MIL-STD-454M, 1989; MIL-HDBK-759B, 1992;
    NASA-STD-3000A, 1989\]

-   **12.4.4.2** **Path to ground.** The path from the ground connection
    to ground shall:

a.  be continuous and permanent,

b.  have ample carrying capacity to conduct safely any currents that may
    be imposed on it,

c.  have impedance sufficiently low to limit the voltage above ground
    and to facilitate the operation of the over-current devices in the
    circuits, and

d.  have sufficient strength to minimize the possibility of ground
    disconnection. \[Source: MIL-STD-454M, 1989\]

-   **12.4.4.3** **Grounding techniques.** If welding is not feasible,
    for example with aluminum chassis, the ground connection of
    equipment shall be attached with a machine bolt, lock washer, and
    nut. \[Source: MIL-HDBK-759B, 1992\]

-   **12.4.4.4** **Nonconductive finishes.** Any nonconductive finish on
    a unit of equipment shall be removed before attaching the ground
    connection. \[Source: MIL-HDBK-759B, 1992\]

-   **12.4.4.5** **Rivet connections.** Ground connections shall not be
    attached with rivets because rivets do not give reliable electrical
    connections. \[Source: MIL-HDBK-759B, 1992\]

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-   **12.4.4.6** **Equipment grounding.** The common ground of equipment
    should connect to a bolt that goes through the enclosure and that is
    clearly marked \"ENCLOSURE GROUND\". An external safety ground strap
    should, in turn, be connected to this bolt. The external safety
    ground strap should be a plated flexible copper strap with a
    current-carrying capacity at least twice as large as the equipment
    requires (see Exhibit 12.4.4.6). \[Source: MIL-HDBK-759B, 1992\]

> []{#__RefHeading___Toc26685380 .anchor}**Exhibit 12.4.4.6** Equipment
> grounding

![](media/image4.wmf){width="3.792361111111111in"
height="2.4611111111111112in"}

-   **12.4.4.7** **Ground connections.** Ground connections to shields,
    hinges, slides, or other mechanical components shall not be used to
    complete electrical circuits. \[Source: MIL-STD-454M, 1989\]

-   **12.4.4.8** **Hinges and slides.** Hinges and slides shall not be
    used for grounding paths. \[Source: MIL-STD-454M, 1989\]

-   **12.4.4.9** **Panels and doors.** Panels and doors that contain
    meters, switches, and test points shall be attached or hinged so
    that they are at the same voltage as the equipment in which they are
    mounted, whether opened or closed. \[Source: MIL-STD-454M, 1989\]

    **Discussion.** A ground is considered satisfactory if the
    electrical connection between the door or panel and the ground
    connection exhibits a resistance of 0.1 ohm or less. A satisfactory
    ground also has sufficient current-carrying capacity to ensure the
    reliable and immediate tripping of equipment over-current protection
    devices.

-   **12.4.4.10** **Ground wire in the cable.** Any external or
    interconnecting cable in which a ground is part of the circuit shall
    include a ground wire in the cable. This ground wire shall be
    terminated at both ends in the same way as the other conductors.
    \[Source: MIL-STD-454M, 1989\]

-   **12.4.4.11** **Cable shields as grounds.** Cable shields shall not
    be used as current-carrying ground connections except with coaxial
    cables. \[Source: MIL-STD-454M, 1989\]

-   **12.4.4.12** **Test equipment.** Test equipment (signal generators,
    amplifiers, and oscilloscopes) that is connected by a plug shall
    have an integral ground prong. \[Source: MIL-HDBK-759B, 1992\]

### 12.4.5 Electrical tools and self-powered equipment

-   **12.4.5.1** **Insulation of tools.** Tools used near high voltages
    shall be insulated. \[Source: MIL-STD-1472F, 1999; NASA-STD-3000A,
    1989\]

-   **12.4.5.2** **Electrical cords.** Electrical hand-held power tools
    shall be designed with three-wire power cords with one wire
    grounded. Portable tools protected by an approved system of double
    insulation or its equivalent may be used without a ground wire when
    approved by the acquisition program office. \[Source: MIL-STD-1472F,
    1999; NASA-STD-3000A, 1989\]

-   **12.4.5.3** **Exposed surfaces of tools.** Electrical hand-held
    power tools shall have exposed surfaces that are either
    nonconducting or are electrically connected to the ground wire.
    \[Source: MIL-STD-1472F, 1999\]

    **Discussion.** Exposed surfaces include cases, grips, handles,
    switches, triggers, chucks, and other surfaces with which
    maintainers might come into contact with during operation.

-   **12.4.5.4** **Same voltage.** All external surfaces of self-powered
    equipment shall be at the same voltage. \[Source: MIL-STD-454M,
    1989\]

## 12.5 Physical hazards

General safety rules for physical hazards are given in this section.
This section focuses on making equipment free of potential physical
hazards to maintainers. Guards, caps, and shields are addressed
specifically.

### 12.5.1 General

-   **12.5.1.1** **Protective devices.** Protective covers, cases, or
    padding shall be used on protrusions or other objects that cannot be
    made completely hazard free. \[Source: NASA-STD-3000A, 1989\]

-   **12.5.1.2** **Carried units.** Components and equipment shall be
    designed so maintainers can carry them without risk of cutting their
    hands on sharp edges. \[Source: MIL-HDBK-759B, 1992\]

-   **12.5.1.3** **Countersunk screws.** Screws shall be countersunk if
    a smooth surface is required. \[Source: UCRL-15673, 1985;
    MIL-HDBK-759B, 1992\]

-   **12.5.1.4** **Exposed edges.** Exposed edges shall be either
    protected by rubber, fiber, or plastic or rounded as follows:

a.  The edges of thin sheets less than 0.5 mm (0.02 in) thick shall be
    rolled or curled as shown in Exhibit 12.5.1.4 (a).

> []{#__RefHeading___Toc26685381
> .anchor}![](media/image5.png){width="2.4895833333333335in"
> height="1.1930555555555555in"}**Exhibit 12.5.1.4 (a)** Rolling edges
> of sheets less than 0.5 mm (0.02 in) thick.

b.  Exposed edges 0.5 to 3.0 mm (0.02 up to 0.12 in) thick shall be
    rounded to a full radius as shown in Exhibit 12.5.1.4 (b).

> []{#__RefHeading___Toc26685382
> .anchor}![](media/image6.png){width="2.3958333333333335in"
> height="1.1354166666666667in"}**Exhibit 12.5.1.4 (b)** Rounding
> exposed edges 0.5 up to 3.0 mm (0.02 up to 0.12 in) thick.

c.  ![](media/image7.png){width="2.3958333333333335in"
    height="1.2652777777777777in"}Exposed edges 3.0 up to 6.4 mm (0.12
    up to 0.25 in) thick shall be rounded to a minimum radius of 1.5 mm\
    (0.05 in) as shown in Exhibit 12.5.1.4 (c).

> []{#__RefHeading___Toc26685383 .anchor}**Exhibit 12.5.1.4 (c)**
> Rounding exposed edges 3.0 to 6.4 mm (0.12 up to 0.25 in) thick.

d.  ![](media/image8.png){width="2.4583333333333335in"
    height="1.6416666666666666in"}Exposed edges 6.4 mm (0.25 in) thick
    or greater shall be rounded to a minimum radius of 3.0 mm (0.12 in)
    as shown in Exhibit 12.5.1.4 (d). \[Source: NASA-STD-3000A, 1989\]

> []{#__RefHeading___Toc26685384 .anchor}**Exhibit 12.5.1.4 (d)**
> Rounding of exposed edges 6.4 mm (0.25 in) thick or greater

-   **12.5.1.5** **Exposed corners.** Exposed corners shall be rounded
    as follows:

a.  ![](media/image9.png){width="2.3958333333333335in"
    height="2.1354166666666665in"}Exposed corners less than 25 mm (1.0
    in) thick shall be rounded to a minimum radius of 13 mm (0.5 in) as
    shown in Exhibit 12.5.1.5 (a).

> []{#__RefHeading___Toc26685385 .anchor}**Exhibit 12.5.1.5 (a)**
> Requirements for rounding of corners less than 25 mm (1.0 in) thick.

b.  ![](media/image10.png){width="2.34375in"
    height="2.354861111111111in"}Exposed corners 25 mm (1.0 in) thick or
    greater shall be rounded to 13 mm (0.5 in) spherical radius, as
    shown in Exhibit 12.5.1.5 (b). \[Source: NASA-STD-3000A, 1989\]

> **Exhibit 12.5.1.5 (b)** Requirements for rounding of corners greater
> than 25 mm (1.0 in) thick.

-   **12.5.1.6** **Projecting components.** In areas where maintainers
    must make rapid movements, small projecting components should be
    avoided or covered. \[Source: MIL-HDBK-759B, 1992\]

    **Discussion.** If small projecting parts (such as toggle switches
    or small knobs) must be mounted on a front panel, recessed mountings
    of these projecting parts are desirable.

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-   **12.5.1.7** **Latches.** Latches or similar devices that can pinch
    fingers shall not be used. \[Source: NASA-STD-3000A, 1989\]

-   **12.5.1.8** **Levers, cranks, hooks, and controls.** Levers,
    cranks, hooks, and controls shall not be located where they can
    pinch, snag, or cut the maintainer or his or her clothing. \[Source:
    NASA-STD-3000A, 1989\]

-   **12.5.1.9** **Burr free.** Exposed surfaces that can be grasped by
    the bare hand shall be free of burrs. \[Source: NASA-STD-3000A,
    1989\]

-   **12.5.1.10** **Capped bolt threads.** Bolts with more than two
    exposed threads shall be capped to protect the maintainer from the
    sharp threads. \[Source: NASA-STD-3000A, 1989\]

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-   **12.5.1.11** **Air-exhaust openings.** Air-exhaust openings used to
    cool equipment should be located so that maintainers are not exposed
    to moving parts or direct drafts. \[Source: MIL-HDBK-759B, 1992\]

### 12.5.2 Guards, caps, and shields

-   **12.5.2.1** **Avoiding accidental contact.** Equipment shall have
    shields and guards to prevent maintainers from accidentally touching
    rotating or oscillating parts such as gears, couplings, levers,
    cams, and large solenoids. \[Source: MIL-HDBK-759B, 1992\]

-   **12.5.2.2** **Enclosure of hazardous components.** Any component
    that rotates, oscillates, or carries high voltage shall be enclosed
    so that maintainers cannot accidentally come in contact with the
    component. \[Source: MIL-HDBK-759B, 1992\]

-   **12.5.2.3** **Ventilation holes.** If a cover or shield requires
    ventilation holes, the holes shall be small enough to prevent
    inadvertent insertion of objects that might touch high voltage
    sources or moving parts. \[Source: AFSC DH 1-3, 1980\]

-   **12.5.2.4** **High-temperature units of equipment.**
    High-temperature units of equipment shall be located, guarded, or
    shielded so that maintainers will not accidentally touch them.
    \[Source: MIL-HDBK-759B, 1992\]

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-   **12.5.2.5** **Guard design.** Guards should be designed and mounted
    so that maintainers do not have to remove them in order to inspect
    components. Guard design and applications should comply, as
    applicable with provisions of OSHA 29 CFR 1910.211 -222 which
    addresses guarding for various industries. \[Source: 29 CFR 1910.211
    --222; MIL-HDBK-759B, 1992\]

## 12.6 Liquid and gas hazards

This section gives rules for maintaining safety near liquid and gas
lines. OSHA 29 CFR 1910.101 -111 address handling of hazardous gases and
liquids including those that are flammable and combustible. Electrical
requirements associated with such hazards are treated.

-   **12.6.1** **Releasing gases.** Equipment shall not release gases
    that combine with the atmosphere to form an acid or corrosive alkali
    that would be detrimental to the health of the maintainer. \[Source:
    Department of Transportation (FAA-G-2100F), 1993; MIL-STD-454M,
    1989\]

-   **12.6.2** **Distinctive types.** Connectors for lines serving
    different functions, for example, fuel lines and water lines, or
    electrical power lines and radio-frequency signal lines, shall be
    distinctively different and physically incompatible. \[Source:
    UCRL-15673, 1985\]

-   **12.6.3** **Automatic shutoffs.** Automatic shutoff devices shall
    be provided on fluid and fuel service equipment to prevent overflow
    and spillage. \[Source: MIL-STD-1472F, 1999\]

-   **12.6.4** **Avoid spraying fluids.** Lines shall be kept from
    spraying or draining fluid on personnel or equipment during
    disconnection by: (1) locating connections away from work areas and
    sensitive components, (2) shielding sensitive components where
    required, and (3) providing drains and bleed fittings so lines can
    be drained or depressurized before they are disconnected. \[Source:
    MIL-HDBK-759B, 1992; UCRL-15673, 1985\]

-   **12.6.5** **Mercury.** Components and equipment containing mercury
    shall not be used unless use of mercury is specifically required or
    approved by the acquisition program office. \[Source: FAA-G-2100F,
    1993; MIL-STD-454M, 1989\]

-   **12.6.6** **OSHA safety criteria for hazardous gases and liquids.**
    Design and handling for hazardous liquids and gases shall be
    governed by OSHA 29 CFR 1910.101 -111. \[Source: 29 CFR 1910.101
    -111\]

## 12.7 Toxic hazards

All reasonable precautions need to be taken to eliminate hazards from
toxic fumes, for example, those from the exhausts of internal combustion
engines. From the standpoint of health hazards, the most widespread
toxic hazards are carbon monoxide from gasoline engines, and aldehydes
and nitrogen oxides from diesel engines. This section gives rules for
keeping toxic hazards within safe limits in the maintainer\'s
environment. OSHA 29 CFR 1910 addresses toxic chemical hazards and their
control. OSHA 29 CFR 1910.1450 addresses controls and exposures in
laboratories. Exposures to cleaning materials is addressed in OSHA 29
CFR 1910.107 and 252. Specific chemical agents, air contaminants and
fibers, and processing operations are covered in OSHA 29 CFR 1910.

-   **12.7.1** **Exposure.** Maintainers shall not be exposed to
    concentrations of toxic substances in excess of the limits specified
    in either OSHA 29 CFR 1910 or the American Conference of
    Governmental Industrial Hygienists Threshold Limit Values. If a
    discrepancy exists between these documents, OSHA 29 CFR 1910 shall
    take precedence. \[Source: 29 CFR 1910; MIL-STD-1472F, 1999;
    Department of Defense (MIL-STD-1800A), 1990; MIL-HDBK-759B, 1992\]

-   **12.7.2** **Carbon monoxide.** Maintainers shall not be exposed to
    concentrations of carbon monoxide (CO) in excess of 50 parts per
    million (ppm) or 55 mg/m^3^. \[Source: 29CFR 1910.100;
    MIL-STD-1472F, 1999; MIL-HDBK-759B, 1992\]

    **Discussion.** Carbon monoxide is particularly dangerous in that it
    is odorless, colorless, and tasteless. Its effects are cumulative;
    doses that may be tolerable by individuals over brief periods may
    prove to be dangerous to them when repeated or prolonged over
    several hours.

    Carbon monoxide combines with the blood to form carboxyhemoglobin
    (COHb). CO accumulates rapidly in the blood, however, the body is
    extremely slow in reducing the COHb level which may account for its
    toxic action. Maximum COHb levels have been set at 5% for all system
    design objectives and aviation system performance limits and at 10%
    for all other system performance.

-   **12.7.3** **Cadmium oxide fumes.** Maintainers shall not be exposed
    to more than 0.1 milligrams of cadmium oxide per cubic meter of air.
    If possible, adequate ventilation shall be provided whenever any
    silver solder is used. If adequate ventilation cannot be supplied,
    maintainers shall be provided with respirators to prevent serious
    exposure to the cadmium oxide fumes. \[Source: Department of
    Transportation (FAA Order 6000.15), 1991\]

    **Discussion.** When a cadmium alloy containing a silver brazing is
    heated appreciably above its melting point, acutely poisonous brown
    or yellow cadmium oxide fumes are released. Inhalation of cadmium
    oxide fumes can result in serious and sometimes fatal damage to
    maintainers.

-   **12.7.4** **Fumes from batteries.** Adequate ventilation shall be
    provided in all battery service facilities. Fumes from batteries can
    be harmful to maintainers both because of the hazards of breathing
    the fumes themselves and because the fumes may displace oxygen.
    \[Source: FAA Order 6000.15B, 1991\]

-   **12.7.5** **Safety for toxic chemicals and materials.** Safety
    design and operation for toxic materials shall be governed by OSHA
    29 CFR 1910.1200 and its appendix A. \[Source: 29 CFR 1910.1200\]

-   **12.7.6** **Asbestos.** Components and equipment containing
    asbestos shall not be used. \[Source: FAA-G-2100F, 1993\]

## 12.8 Radiation hazards

Radiation emitting systems and equipment require special consideration
to minimize hazards to maintainers. Potential hazards arising from
nuclear and electromagnetic radiation need to be evaluated by
specialized personnel trained in investigating and controlling such
hazards. OSHA 29 CFR 1910.96 and .97 address the effects of ionizing and
non-ionizing radiation respectively. This section includes the rules for
radiation hazards. \[Source: 29 CFR 1910.96 and .97; MIL-HDBK-759B,
1992\]

-   **12.8.1** **Radioactive materials.** Use of radioactive materials
    shall conform to Nuclear Regulatory Commission regulations and shall
    require approval of the acquisition program office. \[Source:
    FAA-G-2100F, 1993; MIL-STD-454M, 1989\]

-   **12.8.2** **Radium.** Radium shall not be used for luminosity (for
    example, making components visible in the dark). \[Source:
    FAA-G-2100F, 1993; MIL-STD-454M, 1989\]

-   **12.8.3** **Ionizing radiation exposure.** The radiation measured
    at any external surface of a unit of equipment producing ionizing
    radiation shall not exceed 0.5 milliroentgens per hour (rem) at a
    distance of 50 mm (2 in). Cumulative whole body exposure to
    maintainers shall not exceed 3 rem for any calendar quarter and 5
    rem for any calendar year. The cumulative occupational exposure to
    an employee shall not exceed 5(n-18) rems where n equals the
    individual\'s age at the last birthday. Employees under 18 years of
    age shall not be exposed to over 10 percent of the allowable
    calendar quarter dose. OSHA 29 CFR 1910.96 and 97 shall govern
    protection from and exposure to ionizing and non-ionizing radiation
    respectively. \[Source: 29 CFR 1910.96 and 97; MIL-STD-1472F, 1999;
    MIL-STD-1800A, 1990\]

-   **12.8.4** **Microwave and radio frequency radiation.** Electronic
    equipment or electrical equipment capable of emitting microwave or
    radio frequency radiation between 300 KHz and 100 GHz shall be
    designed, fabricated, shielded, and operated to avoid overexposure
    of maintainers. According to OSHA 29 CFR 1910.97, partial or whole
    body electromagnetic radiation between 10 MHZ and 100GHz shall be
    restricted a maximum of 10mW/cm2 over any 0.1-hour period. Equipment
    design and installation in any unrestricted area accessible to
    maintainers shall meet the requirements of IEEE C95.1. \[Source: 29
    CFR 1910.97\]

## 12.9 Protection from special chemicals

Protection from special chemicals (such as battery electrolyte) cleaning
solvents, Polychlorinated Byphenyls, and carcinogens is addressed in
this section.

-   **12.9.1** **Protection against battery acid.** Maintainers shall be
    provided acid resistant gloves, aprons and face shields that offer
    side as well as frontal protection for protection against the
    splattering of battery acid when they measure storage battery
    specific gravity or when they handle electrolyte. \[Source: 29 CFR
    1926.441; Department of Transportation (FAA Order 3900.19A), 1982\]

-   **12.9.2** **Battery handling area.** Quick drenching facilities
    shall be provided within 25 feet of a battery handling area.
    \[Source: 29 CFR 1926.441; FAA Order 3900.19A, 1982\]

-   **12.9.3** **Large-sized service facilities.** If large quantities
    of electrolyte are handled or a large number of batteries are
    maintained, facilities shall be provided for quick drenching or
    flushing of the eyes and body. \[Source: FAA Order 3900.19A, 1982\]

    **Exception.** If the storage batteries are of the enclosed type and
    the facility is equipped with explosion proof or resistant vents,
    sealed water rinse or neutralizing packs may be used.

-   **12.9.4** **Small-sized service facilities.** If small quantities
    of electrolyte are handled and a small number of batteries are
    maintained, water rinse for flushing of the eyes and body shall be
    provided in place of drenching or flushing facilities. \[Source: FAA
    Order 3900.19A, 1982\]

-   **12.9.5** **Cleaning solvents.** Adequate ventilation shall be
    provided whenever any solvents or cleaners are used. Solvents that
    produce fumes (such as carbon tetrachloride) shall not be used and
    all permissible cleaning solvents shall be stored in safety cans.
    \[Source: FAA Order 6000.15B, 1991\]

    **Discussion.** Inhaled fumes from carbon tetrachloride are
    extremely hazardous to the respiratory system and some may have a
    caustic effect on the skin.

-   **12.9.6** **Polychlorinated Biphenyls (PCBs).** Maintainers shall
    be provided protective clothing when handling PCBs. All PCB items
    (such as transformers, capacitors, hydraulic machinery, and circuit
    breakers) with PCB concentrations of 500 parts per million shall be
    marked, inspected, and disposed of according to FAA Order 1050.14.
    PCBs shall not be used when suitable substitutes are available.
    \[Source: FAA Order 6000.15B, 1991; Department of Transportation
    (FAA Order 1050.14), 1991\]

-   **12.9.7** **Carcinogens.** The use of chemicals that have been
    identified by the Occupational Safety and Health Act (OSHA) as
    cancer producing substances (carcinogens) shall be evaluated and
    conform to OSHA 29 CFR 1910. \[Source: 29 CFR 1910; MIL-STD-454M,
    1989\]

## 12.10 Temperature hazards

Tissue burns can occur when skin temperature reaches 45C (113F). Objects
at temperatures in excess of this can be touched safely, depending on
the: (1) duration of touch, (2) finish and diffusivity of the surfaced
touched, (3) force of contact, and (4) size of contact area. Rules for
equipment related temperature are given in this section.

-   **12.10.1** **\"Touch temperature\" contact.** Equipment that in
    normal operation exposes maintainers to surface temperatures outside
    the range of temperatures shown in Exhibit 12.10.1, shall be
    shielded. Cryogenic systems shall also be shielded. \[Source:
    DOE-HFAC1, 1992; MIL-STD-1472F, 1999; MIL-STD-454M, 1989\]

> []{#__RefHeading___Toc26685387 .anchor}**Exhibit** **12.10.1** Upper
> and lower temperature limit range

-   **12.10.2** **Perforation size.** Cases, covers, and shields that
    are perforated to permit ventilation shall be no larger than 13 mm
    (.050 in) in diameter to prevent inadvertent insertion of objects
    that might touch high voltage sources or moving parts. Many smaller
    perforations are preferable to a few large ones. \[Source:
    MIL-HDBK-759B, 1992\]

## 12.11 Fire Protection

The avoidance and minimization of fire hazards begins with good
housekeeping, which needs to be a personal goal of all maintainers. This
section gives rules for reducing fire hazards. Fire protection
provisions which affect design of facilities and equipment as well as
operations and maintenance are governed by OSHA 29 CFR 1910 Subpart Fire
Protection L (155 -167) Subpart H Hazardous materials (101 -119) and
Associated national consensus standard sponsored by the National Fire
Protection Association and the American National Standard Institute.
OSHA 29 CFR 1910.307 and 308 address electrical installations in
hazardous locations and environments.

-   **12.11.1** **Nonflammable enclosures.** If capacitors, inductors,
    and motors are potential fire hazards, they shall have nonflammable
    enclosures with a minimum number of openings. \[Source:
    MIL-HDBK-759B, 1992\]

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-   **12.11.2** **Flammable materials.** If possible, designers should
    avoid specifying the use of flammable materials in equipment.
    \[Source: MIL-HDBK-759B, 1992\]

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-   **12.11.3** **Flammable gases.** If possible, equipment shall be
    designed so that it will not emit flammable gases during storage or
    operation. If this is not possible, automatic cutoffs and suitable
    warnings shall be provided. OSHA 29 CFR 1910.101 -119 governs
    handling of hazardous materials including those that are flammable,
    combustible, and explosive. \[Source: 29 CFR 1910.101 --119;
    MIL-HDBK-759B, 1992\]

-   **12.11.4** **Fire extinguishers.** Where fire hazards exist,
    portable, hand-operated fire extinguishers shall be located where
    fires will not block their access. \[Source: MIL-HDBK-759B, 1992\]

-   **12.11.5** **Selection of fire extinguishers.** Fire extinguishers
    shall be selected for suitability by the class of fires most likely
    to occur in an area. OSHA 29 CFR 1910.157 governs the selection and
    use of fire extinguishers. \[Source: 29 CFR 1910.157; MIL-HDBK-759B,
    1992\]

    **Discussion.** Class A fires involve ordinary flammable materials
    such as wood, paper, and rags that can be extinguished with water or
    aqueous solutions. Class B fires involve flammable liquids such as
    gasoline, solvents, and greases that can be extinguished by
    dilution, elimination of air, or blanketing. Class C fires involve
    electrical equipment such as motors, transformers, and switches that
    need to be extinguished by a substance that does not conduct
    electricity.

-   **12.11.6** **Fire protection criteria.** OSHA 29 CFR 1910 Subpart L
    Fire protection (155 -165); Subpart H Hazardous materials (101 -119)
    and associated national consensus standards sponsored by the
    National Fire Protection Association and the American National
    Standards Institute shall govern the fire protection aspects for
    maintenance of facilities and equipment. OSHA 29 CFR 1910.307 -308
    governs electrical installations in hazardous locations and
    environments. \[Source: 29 CFR 1910.307 -308\]

## 12.12 Noise hazards 

Noise can be hazardous to maintainers in two general ways: it can cause
hearing loss, both temporary and permanent, and it can prevent
maintainers from hearing audible warning signals. Rules are given in
this section to protect maintainers from these hazards. Rules concerning
administrative and engineering controls to reduce noise and a hearing
conservation program are given in Chapter 13.5.

-   **12.12.1 General noise levels.** Workplace noise shall be
    maintained at levels that will not (1) interfere with necessary
    voice, telephone, and radio communication, (2) cause fatigue or
    injury, or (3) degrade overall system effectiveness. \[Source:
    MIL-STD-1800A, 1990\]

-   **12.12.2 Noise** **criteria.** Noise criteria are defined by either
    the A-weighted sound level, dB(A), or the speech interference level
    (SIL). The A-weighted sound level is the desired requirement. Where
    it is not possible to meet the specified A-weighted sound level, the
    corresponding SIL requirement shall be met. \[Source: MIL-STD-1800A,
    1990\]

    **Definitions. Preferred speech interference level (PSIL-4)** is a
    measure of the effectiveness of noise in masking speech. **Speech
    interference level (SIL or SIL-4)** is the arithmetic mean, in dB
    (or 20Pa), of sound pressure levels in the four octave bands with
    center frequencies of 500, 1000, 2000, and 4000 Hz. **A-weighted
    sound level** **(dB(A))** is a sound pressure level (in decibels)
    measured using a sound level meter with an A-weighting network. The
    A-weighted response is maximum at 2500 Hz, drops rapidly as
    frequency decreases below 1000 Hz, and gradually decreases above
    4000 Hz, thereby approximating the frequency dependent human
    response to moderate sound levels. ANSI S1.4 gives the definition of
    A-weighting filter characteristics.

-   **12.12.3** **Extreme quiet areas.** Ambient noise in areas
    requiring extreme quiet shall not exceed 35 dB(A) or 27 dB PSIL-4.
    \[Source: MIL-HDBK-759B, 1992\]

-   **12.12.4** **Small office spaces and special areas.** Ambient noise
    in areas requiring no difficulty with speech communication (for
    example, libraries and classrooms) shall not exceed 45 dB(A) or 37
    dB PSIL-4; conference rooms and offices shall not exceed 38 dB
    PSIL-4. \[Source: FAA-G-2100F, 1993; MIL-HDBK-759B, 1992\]

-   **12.12.5** **Operational areas.** Ambient noise in areas requiring
    frequent phone use or requiring occasional speech communication (for
    example, operations centers, control rooms, tower cabs, and dynamic
    simulation rooms) at distances up to 4.6 m (15 ft) shall not exceed
    55 dB(A) or 47 dB PSIL-4; shop offices and laboratories shall not
    exceed 48 dB PSIL-4. \[Source: FAA-G-2100F, 1993; MIL-HDBK-759B,
    1992\]

-   **12.12.6** **Equipment areas.** Ambient noise in areas requiring
    frequent telephone use or frequent speech communication (for
    example, computer rooms, engineering areas, equipment rooms, and
    telephone switching centers) at distances up to 1.5 m (5 ft) shall
    not exceed 65 dB(A) or 57 dB PSIL-4. \[Source: FAA-G-2100F, 1993;
    MIL-HDBK-759B, 1992\]

-   **12.12.7** **High noise, remote areas.** High noise, remote areas
    that are normally unmanned shall not exceed 85 dB(A). \[Source:
    FAA-G-2100F, 1993\]

-   **12.12.8** **Occupational** **noise exposure and control.**
    Administrative or engineering controls shall be used to reduce the
    sound levels to within permissible noise exposure levels listed in
    Exhibit 12.12.8. OSHA 29 CFR 1910.95 shall be used in determining
    equivalent A-weighted sound levels for daily exposure. A hearing
    conservation program shall be administered any time an employee\'s
    noise exposure equals or exceeds an 8-hour time weighted average of
    85 db measure on the A scale (slow response) or equivalent without
    regard to attenuation that may be provided by personal protective
    equipment. OSHA 29 CFR 1910.95 shall govern the hearing protection
    program. \[Source: 29 CFR 1910.95\]

> []{#__RefHeading___Toc26685388 .anchor}**Exhibit 12.12.8** Permissible
> noise exposure

##  

## 12.13 Explosion and implosion hazards

Maintainers are sometimes exposed to risks of explosion (for example,
the presence of explosive gases), or of implosion (for example, a
scratched cathode ray tube (CRT). Rules are given in this section to
protect the maintainer from such hazards.

-   **12.13.1** **CRT conformance.** CRTs shall conform to the
    requirements of UL 1418. \[Source: MIL-HDBK-759B, 1992;
    MIL-STD-454M, 1989\]

-   **12.13.2** **Terminal end of CRT.** Whenever possible, the terminal
    end of CRTs shall be located within the equipment housing. If the
    terminal end extends outside the equipment housing, it shall have a
    cover strong enough to protect the tube. This cover shall be
    anchored to the main housing structure firmly enough to withstand
    shipping and rough handling so that external pressures will not be
    transmitted to the tube and its wiring. There shall also be a
    warning inside the equipment informing maintainers that the neck of
    the tube is fragile and must be handled with caution. \[Source:
    MIL-HDBK-759B, 1992\]

-   **12.13.3** **Explosion.** Equipment that may be operated,
    maintained, or stored in an explosive atmosphere shall be designed
    to eliminate the possibility of an explosion. \[Source:
    MIL-HDBK-759B, 1992\]

-   **12.13.4** **Minimizing risk of explosion.** Risk of explosion
    shall be minimized by isolating hazardous substances from heat
    sources and by using spark arrestors, vents, drains, or other safety
    techniques. \[Source: MIL-HDBK-759B, 1992\]

-   **12.13.5** **Explosion causing gases.** Materials shall not
    liberate gases that will produce an explosive atmosphere. \[Source:
    MIL-STD-454M, 1989\]

## 12.14 Radiant energy hazards 

This section gives rules for radiant energy (200 nm to 1 m) hazards.
This range covers ultraviolet through microwave radiant energy.

### 12.14.1 Ultraviolet radiant energy (200-315 nm) 

-   **12.14.1.1** **Exposure limit.** The maximum daily radiant energy
    exposure to ultraviolet light (200-315 nm) shall not exceed an
    effective value of 0.003 J/cm^2^. \[Source: Farrell & Booth, 1975\]

    **Discussion.** The equations and tables shown in Exhibit 12.14.1.1
    can be used to convert irradiance measured in each part of the
    spectrum to total effective irradiance.

    **Definition. Irradiance** is the radiant flux density on a given
    surface.

> []{#__RefHeading___Toc26685389 .anchor}**Exhibit 12.14.1.1** Exposure
> limit for ultraviolet radiant energy (200 to 315 mm)

### 12.14.2 Near-ultraviolet radiant energy (315-400 nm)

-   **12.14.2.1** **Exposure duration greater than 1000 seconds.** The
    maximum radiant energy exposure to near ultraviolet light (315-400
    nm) shall not exceed 0.001 W/cm^2^ for exposure durations longer
    than 1000 sec. \[Source: Farrell & Booth, 1975\]

-   **12.14.2.2** **Exposure duration less than 1000 seconds.** The
    maximum radiant energy exposure limit to near ultraviolet light
    (315-400 nm) shall not exceed 1 J/cm^2^ in any 1000-second period.
    \[Source: Farrell & Booth, 1975\]

### 12.14.3 Visible and near-infrared radiant energy (400-1400 nm)

Visible and near-infrared radiant energy, with a wavelength of 400 to
approximately 1400 nm, is largely transmitted by the ocular media of the
eye and absorbed at the retina. Unlike corneal injury from ultraviolet
energy, injury to the retina is generally permanent. As a result,
special care must be taken to avoid retinal damage. \[Source: Farrell &
Booth, 1975\]

If appropriate image spectral radiance data are not immediately
available, it may be helpful to estimate whether a particular image
luminance exceeds permissible exposure limits. The relationship between
luminance and radiance has been published for typical lamps, but these
values cannot be used directly because radiant energy with a wavelength
greater than 700 nm is less effective in heating the retina.

If the spectral distribution of radiant energy in the displayed image is
known, the luminosity function for the eye (see Exhibit 12.14.3) can be
used to calculate the ratio between luminance and effective radiance,
and hence, the permissible luminance. This process is illustrated here
for three hypothetical equal-energy-per-wavelength sources that differ
in wavelength range.

> []{#__RefHeading___Toc26685390 .anchor}**Exhibit 12.14.3** Relative
> contribution of different wavelengths to luminance --the luminosity
> function

![](media/image11.png){width="4.697222222222222in"
height="3.5743055555555556in"}

-   **12.14.3.1** **Exposure of the eye.** The maximum radiant energy
    exposure to visible and near-infrared light (400-1400 nm) shall not
    exceed the limits given in Exhibit 12.14.3.1. These limits apply to
    any source larger than 1. \[Source: Farrell & Booth, 1975\]

    **Note.** For wavelengths longer than 700 nm, a correction factor,
    K, is required to compensate for the increase in absorption in the
    ocular media and the decrease in absorption by the retina.

> []{#__RefHeading___Toc26685391 .anchor}**Exhibit 12.14.3.1** Maximum
> safe exposure to 400-1400 nm radiant energy.\
> ![](media/image12.png){width="4.336111111111111in"
> height="2.7708333333333335in"}

-   **12.14.3.2** **Exposure of skin.** The maximum radiant energy
    exposure of a maintainer\'s skin to visible and near-infrared light
    (400-1400 nm) shall not exceed 0.2 W/cm^2^. \[Source: Farrell &
    Booth, 1975\]

-   **12.14.3.3** **Removing infrared.** If infrared radiant energy
    exceeds the allowable limit, filters shall be provided to protect
    the maintainer\'s eyes from unnecessary heat. \[Source: Farrell &
    Booth, 1975\]

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-   **12.14.3.4** **Maximum display.** High-luminance displays should
    not exceed 242 lumens per effective watt of the 400 to 700 nm source
    (see Exhibit 12.14.3.4). \[Source: Farrell & Booth, 1975\]

**Definition.** An **effective watt** is equal to 1.84 watts.

**Exhibit 12.14.3.4** Estimation of permissible image luminance

### 12.14.4 Far-infrared radiant energy (1400-10^6^ nm) 

-   **12.14.4.1** **Short term exposure.** The maximum radiant energy
    exposure to far-infrared light (1400-10^6^ nm) for 60-120 seconds
    shall not exceed 0.1 W/cm^2^. A measurement aperture of 1 mm (0.04
    in) shall be used for wavelengths shorter than 10^5^ nm, and an
    aperture of 11 mm (0.43 in) shall be used for longer wavelengths.
    \[Source: Farrell & Booth, 1975\]

-   **12.14.4.2** **Chronic exposure.** The maximum chronic radiant
    energy exposure to far-infrared light (1400-10^6^ nm) shall not
    exceed 0.01 W/cm^2^. A measurement aperture of 1 mm (0.04 in) shall
    be used for wavelengths shorter than 10^5^ nm, and an aperture of 11
    mm (0.43 in) shall be used for longer wavelengths. \[Source: Farrell
    & Booth, 1975\]

### 12.14.5 Microwave radiant energy (10^7^-10^11^ Hz) 

-   **12.14.5.1** **Exposure limit.** The maximum radiant energy
    exposure to microwave radiation (10^7^-10^11^ Hz, which corresponds
    to wavelengths of 1 mm (0.04 in) to 1 m (39.37 in)) shall be no more
    than 0.01 W/cm^2^ averaged over a 0.1-hour period. \[Source: Farrell
    & Booth, 1975\]

## 12.15 Laser hazards

This section gives rules for protecting the maintainer from laser
hazards.

-   **12.15.1** **Laser radiation.** Laser equipment and system design,
    installation, and operational and maintenance procedures shall
    conform to OSHA 21 CFR 1040. \[Source: 21 CFR 1040; Farrell & Booth,
    1975\]

-   **12.15.2** **Laser exposure limits.** In accordance with OSHA 29
    CFR 1926.54 (j), employees shall not be exposed to laser light
    intensities above:

a.  Direct staring: 1 microwatt per square centimeter.

b.  Incidental observing: 1 milliwatt per square centimeter.

c.  Diffuse reflected light: 2 1/2 watts per square centimeter.

**Discussion**. For safety reasons, laser units need to be set up to
operate above head level of employees, when possible. \[Source: 29 CFR
1926.54 (j)\]

-   **12.15.3** **Eye protection from laser light.** OSHA 29 CFR 1926.54
    shall govern potential exposure areas to direct or reflected laser
    light. Employees shall be provided with antilaser eye protection
    devices if any such exposure to laser light greater than 5
    milliwatts exists. OSHA 29 CFR 1926.102 (b)(2) shall govern optical
    density of the eye protection based upon the maximum power density
    and specific wavelength of the laser. \[Source: 29 CFR 1926.54\]

-   **12.15.4** **Labeling of laser protective goggles.** OSHA 29 CFR
    1926.102 (b)(2)(ii) shall govern the labeling laser optical
    protection devices. Labels shall include the following:

a.  Laser wavelengths for intended use.

b.  Optical density of those wavelengths.

c.  The visible light transmission. \[Source: 29 CFR 1926.102
    (b)(2)(ii)\]

-   **12.15.5** **Laser alignment.** In accordance with OSHA 29 CFR
    1926.54 (f) only mechanical or electronic means shall be used as a
    detector for guiding the internal alignment of a laser. \[Source: 29
    CFR 1926.54\]

## 12.16 Safety labels and placards

This section contains rules for the labeling and placing of placards on
hazardous components, equipment, and systems. Use of these rules will
help to ensure the safety of maintainers and equipment.

-   **12.16.1** **Warning** **labels and placards.** Labels or placards
    shall be placed on or adjacent to any equipment that presents a
    hazard (for example, high voltage, heat, toxic vapors, explosion,
    and radiation) to maintainers. These labels or placards shall
    describe the hazard and state precautions the maintainer can take.
    \[Source: MIL-STD-1472F, 1999; MIL-HDBK-759B, 1992; DOE-HFAC1, 1992;
    NASA-STD-3000A, 1989; MIL-STD-454M, 1989\]

-   **12.16.2** **Label and placard design.** Labels and placards shall
    consist of three panels as shown in Exhibit 12.16.2. The ratio of
    width to height of the upper panel (a:b) shall fall within the range
    of 2:1 to 5:1 inclusive. The lower panel width shall be equal to the
    upper panel width (both equal to a). The lower panel height shall be
    equal to or greater than the upper panel height, but less than twice
    the width of the sign (b ó c \< 2a). The optional symbol panel shall
    be square with its edge equal to the sum of the upper and lower
    panel (b + c) and placed to the right of the upper and lower panels.
    The upper panel shall contain the signal or key work. the lower
    panel shall contain additional direction or explanation. Wording of
    this panel shall be brief, provide positive direction (if possible),
    and be limited to a single hazard. \[Source: MIL-STD-1472F, 1999\]

> ![](media/image14.png){width="4.750694444444444in"
> height="2.1847222222222222in"}[]{#__RefHeading___Toc26685393
> .anchor}**Exhibit 12.16.2** Label and placard layout --two panel sign
> with optional symbol panel

-   **12.16.3** **Label** **and placard design classifications and
    specifics.** Signs shall have one of four classifications:

a.  Class I (Danger). Danger labels and placards indicate immediate and
    grave danger or peril, a hazard capable of producing irreversible
    damage or injury, and prohibitions against harmful activities. These
    signs shall have the word \"DANGER\" in white within a red oval
    outline with a white on black rectangle in the upper panel. The
    lower panel, for additional wording, shall be in black or red on a
    white background.

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```
b.  Class II (Caution). Caution labels and placards are used to call
    attention to potential danger or hazard, or a hazard capable of, or
    resulting in severe but not irreversible injury or damage. These
    signs shall have the signal word \"CAUTION\" in yellow on a black
    rectangle in the upper panel. The lower panel, for additional
    wording, shall be in black on a yellow background.

c.  Class III (General safety). General safety labels and placards
    include notice of general practice and rules relating to health,
    first aid, housekeeping, and general safety other than the two cases
    above. These signs shall have the appropriate key word in white on a
    green rectangle in the upper panel. The lower panel, for additional
    wording, shall be in black or green on a white background.

d.  Class IV (Fire and emergency). Fire and emergency labels and
    placards shall be used only to label or point the way to fire
    extinguishing equipment, shutoffs, emergency switches, and emergency
    procedures. These signs shall have the key word in white on a red
    rectangle in the upper panel. The lower panel, for additional
    wording, shall be in red on a white background. \[Source:
    MIL-STD-454M, 1989\]

-   **12.16.4** **Label and placard placement.** Labels and placards
    shall be placed so as to alert and inform in sufficient time to
    avoid the hazard or to take appropriate action. They shall be: (1)
    readable from a distance, (2) create no additional distractions,
    or (3) be hazardous themselves. \[Source: MIL-HDBK-759B, 1992;
    MIL-STD-454M, 1989\]

-   **12.16.5** **Illumination for warning labels and placards.**
    Warning labels and placards shall be visible under the conditions in
    which the maintainer needs to see them. Special illumination may be
    needed to meet this criterion. \[Source: MIL-STD-454M, 1989\]

-   **12.16.6** **Wording for medium voltage labels and placards.** If a
    voltage between 70 and 500 volts is present, a caution label or
    placard shall be provided that includes the following statement or
    its equivalent: \"CAUTION (insert maximum voltage) VOLTS.\" The
    label or placard shall be in accordance with ANSI Z535.2. \[Source:
    MIL-STD-454M, 1989\]

-   **12.16.7 Wording for high voltage labels and placards.** If a
    voltage in excess of 500 volts is present, a warning label or
    placard shall be provided that includes the following statement or
    its equivalent: \"DANGER \-- HIGH VOLTAGE (insert maximum voltage)
    VOLTS.\" The label or placard shall be in accordance with ANSI
    Z535.2. \[Source: MIL-STD-454M, 1989\]

-   **12.16.8** **Microwave or rf radiation warning labels and
    placards.** Each unit of equipment that can emit microwave or rf
    radiation levels between 300 KHz and 100 GHz shall have a warning
    label or placard. This warning label or placard shall be in
    accordance with ANSI Z535.2 and ANSI C95.2. Labels shall be provided
    on all radiation shields and covers to warn maintainers of the
    radiation hazards involved upon removal. \[Source: MIL-STD-454M,
    1989\]

-   **12.16.9** **X radiation shield labels or placards.** Shields that
    protect maintainers from X radiation shall have labels or placards
    in accordance with OSHA 10 CFR 20. \[Source: 10 CFR 20; DOE-HFAC1,
    1992; MIL-STD-1472F, 1999\]

-   **12.16.10** **Ionizing radiation symbols.** Ionizing radiation
    hazard symbols shall be in accordance with ANSI N2.1. \[Source:
    DOE-HFAC1, 1992; MIL-STD-1472F, 1999\]

-   **12.16.11** **Laser warning labels and placards.** Laser warning
    labels and placards shall be in accordance with OSHA 21 CFR 1040
    unless a unit of equipment has been certified as exempt. In
    accordance with OSHA 29 CFR 1926.54 (d) all areas on which lasers
    are used shall be posted with standard laser warning placards.
    \[Source: 21 CFR 1040; MIL-STD-1472F, 1999; DOE-HFAC1, 1992\]

    **Discussion.** If a piece of equipment is exempt, the unit of
    equipment shall have a label or placard that states: CAUTION\--This
    electronic product has been exempted from FDA radiation safety
    performance standards, as prescribed in the Code of Federal
    Regulations, Title 21, Chapter I, Subchapter J, pursuant to
    Exemption No. 76 EL-01 DOD issued on 26 July 1976. This product
    shall not be used without adequate protective devices or procedures.

-   **12.16.12** **Line identification.** Liquid and gas lines shall be
    clearly and unambiguously labeled or coded as to contents, pressure,
    heat, cold, or other hazardous properties in accordance with
    MIL-STD-1247. \[Source: MIL-HDBK-759B, 1992; MIL-STD-1800A, 1990\]

-   **12.16.13** **Electrical labels and placards.** If appropriate, all
    receptacles shall be marked with their voltage, phase, and frequency
    characteristics. \[Source: MIL-STD-1472F, 1999; MIL-HDBK-759B, 1992;
    DOE-HFAC1, 1992\]

-   **12.16.14** **Center of gravity.** If the unit has a high center of
    gravity or if the weight of a unit of equipment is not evenly
    distributed, the center of gravity shall be clearly marked.
    \[Source: MIL-STD-1472F, 1999; DOE-HFAC1, 1992\]

-   **12.16.15** **Weight labels.** Weight and center of gravity caution
    placards shall be placed on any unit of equipment to be moved for
    maintenance if its weight exceeds 13.6 kg (30 lbs.). If it is
    designed to be lifted or carried by more than one person, the label
    shall include the number of people recommended to lift or carry it.
    \[Source: MIL-STD-1472F, 1999; DOE-HFAC1, 1992\]

-   **12.16.16** **Weight lifting capacity.** Weight lifting capacity
    shall be indicated on stands, hoists, lifts, jacks, and similar
    weight-bearing equipment, to prevent possible overloading. \[Source:
    MIL-STD-1472F, 1999; DOE-HFAC1, 1992\]

[]{#__RefHeading___Toc26951006 .anchor}Glossary

**Effective watt** - Equal to 1.84 watts.

**Interlocks** - Devices (for example, switches) connected with a cover,
shield, or case that disable the associated internal hazard (usually
electrical) when the cover, shield, or case is opened. OSHA regulations
discuss lockout and tagout procedures to be used in the workplace during
maintenance or operations to protect from electrical hazards.

**Irradiance** - The radiant flux density on a given surface.

**Lockout** - Uses a mechanical mean to disable a control or switch in
its safe position (for example, electricity disconnected) and to prevent
its activation without the use of undue force or tools.

**N** - Is a metric term for the force measure called a Newton. One
pound force in the English measurement system is equal to 4.4482 Newton
(1 lbf = 4.4482 N).

**Preferred speech interference level (PSIL-4)** - A measure of the
effectiveness of noise in masking speech.

**Speech interference level (SIL or SIL-4)** - The arithmetic mean, in
dB (or 20Pa), of sound pressure levels in the four octave bands with
center frequencies of 500, 1000, 2000, and 4000 Hz.

**Tagouts** - Tags that are attached to a control or place of hazard
associated with an ongoing mode of operation or maintenance.

**Weighted sound level** **(dB(A))** - A sound pressure level (in
decibels) measured using a sound level meter with an A-weighting
network. The A-weighted response is maximum at 2500 Hz, drops rapidly as
frequency decreases below 1000 Hz, and gradually decreases above 4000
Hz, thereby approximating the frequency dependent human response to
moderate sound levels. ANSI S1.4 gives the definition of a-weighting
filter characteristics.

[]{#__RefHeading___Toc26951007 .anchor}References

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<http://www.ansi.org/>

American National Standards Institute. (1993). *Environmental and
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and health regulations for construction (OSHA) (29 CFR 1926) Government
Printing Office.

[]{#__RefHeading___Toc26951008 .anchor}Index

A

Air-exhaust openings 12-19

Alarm device 12-1

Ambient noise 12-27

Aprons, safety 12-23

Asbestos 12-21

Automatic shutoff 12-20, 12-25

B

Batteries 12-21

Battery 12-23

Battery acid, protection 12-23

Bleeders 12-12

C

Cadmium oxide fumes 12-21

Capacitors, inductors, motors 12-25

Caps 12-19

Carbon monoxide 12-21

Carcinogens 12-24

Cases, covers, guards, and shields 12-24

Caution

label 12-37

Chemicals,special 12-23

Cleaning solvent safety 12-23

Color 12-6

Controls 12-19

Cranks 12-19

CRT

hazard 12-29

D

Danger

label 12-37

De-icing 12-5

Discharge capacitors 12-12

E

Electric shock 12-7

protection from 12-8

Electrical equipment near flammable gasses 12-11

Electrical hazards

discharging devices 12-12

grounding 12-13

switches 12-11

Electrical installation, design and location 12-11

Electrical tools 12-15

Emergency exits 12-3

Equipment location 12-6

Equipment stability 12-6

Equipment with wheels 12-6

Equipment-related safety 12-6

Explosion hazards 12-29

Exposed corners 12-18

Exposed edges 12-17

Eye protection 12-34

F

Face shields 12-23

Fail safe 12-9

Fire extinguishers 12-25

Fire hazard reduction 12-25

Fluid lines 12-20

G

Gases 12-20, 12-25, 12-29

Gloves, protective 12-9

Grounding 12-13, 12-14, 12-15

Guard design 12-19

Guard screen 12-5

Guardrail 12-5

Guards 12-19

H

Handholds 12-4, 12-5

fixed 12-5

nonfixed 12-5

Hazard alerting device 12-1

Hazardous components 12-19

Hazards

gas 12-20

liquid 12-20

High temperature 12-19

Hooks 12-19

Hot leads 12-11

I

Illumination 12-4

Implosion hazards 12-29

Insulating equipment 12-8

Interlocks 12-8

bypassable 12-10

non-bypassable 12-10

override 12-10

Irradiance 12-30

L

Labels

warning 12-35, 12-37

wording 12-37

Labels, safety 12-9

Ladders 12-4

Laser 12-35

Laser exposure limits 12-34

Laser hazards 12-34

Latches 12-18

Levers 12-19

Locking control 12-6

Lockout 12-8

M

Main power switch 12-11

Mercury 12-20

Microwave radiant energy 12-34

N

Noise 12-28

Noise hazards 12-26

Noise levels 12-26

Nonskid surfaces 12-3

O

Open gratings, platforms or flooring 12-5

P

Panels and doors 12-15

Perforation size 12-24

Personnel energy

radiant energy 12-31

Personnel safety 12-1

aprons 12-23

carcinogens 12-24

chemicals 12-23

electrical hazards 12-7

eye protection 12-23

fire protection 12-25

gas hazards 12-20

laser hazards 12-34

liquid hazards 12-20

noise hazards 12-26

physical hazards 12-16

radiation hazards 12-22

safety labels and placards 12-35

temperature hazards 12-24

toxic hazards 12-20

work space safety 12-1

Physical barriers 12-2

Physical hazard prevention 12-16

Physical hazards 12-16

Placards 12-35

Platform 12-5

Platforms 12-4

Plugs and receptacles 12-11

Polychlorinated Biphenyls (PCBs) 12-23

Preferred speech interference level 12-26

Protective gloves 12-9

R

Radiant energy 12-30

chronic exposure 12-34

exposure 12-31

eye exposure 12-32

far-infrared 12-33

short term exposure 12-33

Radiant energy hazards 12-29

Radio frequency voltage 12-11

Radioactive materials 12-22

Ramp loads 12-6

Ramps 12-4

Removing power 12-13

Retinal damage 12-31

S

Safety labels 12-35

Screws 12-16

Self powered equipment 12-15

Self-locking device 12-4

Shields 12-19

Shorting rods 12-12, 12-13

Sound level 12-26

Speech interference level 12-26

Stairs 12-4

Static buildup 12-9

Stored energy devices 12-6

Switch box 12-12

Switches 12-11

T

Tagouts 12-8

Telescoping ladders 12-5

Test equipment 12-15

Toe board 12-5

Tool insulation 12-15

Tools 12-15

Touch temperature contact 12-24

V

Ventilation holes 12-19

Voltage guarding 12-10

W

Warning *See* Labels:warning

Wording *See* Labels:wording

Workspace safety 12-1