(a)Protection against explosion hazards. Unless properly
designed, class 1 lamps present two sources of probable explosion hazards:
Ignition of an explosive atmosphere by the heated filament of the bulb in
case the bulb glass is accidentally broken, and ignition by electric sparks
or arcs from the battery or connections thereto. MSHA's therefore, requires
the following safeguards:
(1)Safety device or design. The lighting unit shall have
a safety device to prevent the ignition of explosive mixtures of methane and
air if the bulb glass surrounding the filament is broken. Alternatively, if
the lamp is designed and constructed of materials that will prevent the
ignition of explosive mixtures of methane and air by protecting the bulb from
breakage and preventing exposure of the hot filament, no separate safety
device is required. Alternative designs will be evaluated by mechanical
impact tests, temperature tests and thermal shock tests to determine that the
protection provided is no less effective than a safety device.
(2)Safety device (protection).
The design of the safety device and the housing which protects it shall
be such that the action of the safety device is positive; yet the lamp shall
not be too readily extinguished during normal service by the unnecessary
operation of the device.
(3)Locks or seals. For lamps other than flashlights, all
parts, such as bulb housing and battery container, through which access may
be had to live terminals or contacts shall be adequately sealed or equipped
with magnetic or other equally reliable locks to prevent opening by
unauthorized persons. For flashlights, provision shall be made for sealing
the battery container.
(4)Battery current restricted. Unless all
current-carrying parts including conductors, are adequately covered and
protected by the sealed or locked compartments, the maximum possible current
flow through that part shall be limited by battery design, or by an
enclosed-type fuse inside the sealed or locked container, to values that will
not produce sparks or arcs sufficient to ignite an explosive mixture of
methane and air.
(b)Protection against bodily hazard. This hazard is chiefly due to
the possible burning of the user by electrolyte spilled from the battery.
MSHA, therefore, requires that:
(1)Spilling of electrolyte. The lamp shall be so designed
and constructed that when properly filled the battery will neither leak nor
spill electrolyte under conditions of normal use. Lamps passing a laboratory
spilling test will be considered satisfactory in this respect, contingent
upon satisfactory performance in service.
(2)Corrosion of battery container. The material of which
the container is made shall resist corrosion under conditions of normal
[Sched. 10C, May 17, 1938, as amended at 5 FR 3467, Aug. 30, 1940; 54 FR
30513, July 20, 1989]