Chapter 2. Gassy And Extrahazardous Tunnels of California Labor Code >> Division 5. >> Part 9. >> Chapter 2.
Any tunnel or underground mine classified by the division as
gassy shall operate under special procedures adopted by the board, as
well as rules, regulations, special orders, or general orders for
nongassy underground mines and tunnels.
In any tunnel classified as gassy by the division, there
shall be tests for gas or vapors taken prior to each shift and at
least hourly during actual operation. If a mechanical excavator is
used, gas tests shall be made prior to removal of muck or material
and before any cutting or drilling in tunnels or underground mines
where explosives are used. A log shall be maintained for inspection
by the division showing results of each test. Whenever a tunnel
excavation or underground mine operation approaches a geologic
formation in which there is a likelihood of encountering gas or
water, a probe hole at least 20 feet ahead of the tunnel face or area
where material is being mined shall be maintained.
Whenever gas levels in excess of 10 percent of the lower
explosive limit are encountered initially in a tunnel or underground
mine classified as gassy, the division shall be notified immediately
by telephone or telegraph. The chief of the division or his
authorized representative may waive subsequent notification for gas
readings less than 20 percent of the lower explosive limits upon a
finding that adequate ventilation and other safety measures are
provided to assure employee safety.
In any gassy tunnel or underground mine, the division may
order work halted until adequate testing can be completed to
determine the level of hazard from gases or vapors. A notice of such
shutdown shall be filed by the division inspector with his superiors
as soon as practicable. Any overruling of such order must be made by
the chief or his designated representative and must be in writing. An
onsite inspection must be made by the person overruling an inspector'
s order prior to resumption of work.
In any gassy tunnel or underground mine the division shall
review plans for electrical lighting and power for equipment. When it
is necessary for safety, the inspector may require changes in the
amount and type of lighting, and may require permissive-type wiring,
switches, tools, and equipment.
In any tunnel or underground mine classified gassy, smoking
shall be prohibited and the employer shall be responsible for
collecting all personal sources of ignition such as lighters and
matches from employees entering the tunnel.
Whenever there is any ignition of gas or vapor in a tunnel or
underground mine, all work shall cease, employees shall be removed,
and reentry except for rescue purposes shall be prohibited until the
division has conducted an inspection and authorized reentry for
maintenance or production in writing.
If the level of gas in any tunnel or underground mine reaches
20 percent of its lower explosive limit at any time all men shall be
removed, the division notified immediately by telephone or telegram,
and no one shall reenter the tunnel or underground mine until
approval is given by the division.
In any tunnel or underground mine classified as gassy, all
employees shall be informed of any special orders made by the
division following an inspection. Such notice shall be given before
entering the tunnel or underground mine. A copy of any orders
subsequently written by the division shall be posted and all
employees shall be notified at a safety meeting called by the safety
representative before they are permitted to start work.
In any tunnel classified as gassy by the division,
ventilation shall include continuous exhausting of fumes and air,
unless an alternative ventilation plan which is as effective or
better is approved by the division. Fans for this purpose shall be
located at the surface, and shall be reversible from a single switch
at the portal or shaft. These requirements shall not preclude the use
of auxiliary fans to supply more air or greater exhaust to a tunnel
or underground mine.
A "kill" button capable of cutting off all electrical
equipment shall be maintained in any gassy tunnel or underground
mine. The safety representative or his designated representative
shall cut off power at any time gas or vapor levels reach 20 percent
of the lower explosive limit or more. Before work is restarted every
employee underground shall be informed of the level of gas or vapor
recorded, and a permanent record shall be called to the surface and
retained in a special log.
In any tunnel or underground mine classified as gassy, the
division shall determine the number of fire extinguishers necessary
and their locations.
Any tunnel or underground mine classified as extrahazardous
by the division shall comply with the provisions for gassy tunnels in
this chapter, as well as regulations, rules, special orders, and
general orders of the division or board.
In any extrahazardous tunnel or underground mine smoking by
employees or open flame shall be prohibited. Welding or cutting with
arc or flame underground in other than fresh air shall be done under
the direct supervision of qualified persons who shall test for gas
and vapors before welding or cutting starts and continuously during
such an operation. No cutting or welding shall be permitted in
atmospheres where any concentration of gas or vapor reaches 20
percent of the lower explosive limit or more while a probe hole is
being drilled or when the tunnel face or material from a mine is
In tunnels or underground mines classified extrahazardous,
sufficient air shall be supplied to maintain an atmosphere of all of
the following conditions:
(a) Not less than 19 percent oxygen.
(b) Not more than 0.5 percent carbon dioxide.
(c) Not more than 5 parts per million nitrogen dioxide.
(d) No petroleum vapors or other toxic gases in concentrations
exceeding the threshold limit values established annually by the
American Conference of Governmental Industrial Hygienists.
All electrical equipment and machines, including diesel
engines, used in tunnels or underground mines classified
extrahazardous shall be permissible equipment. The division may,
however, permit the use of nonpermissive equipment in a tunnel or
underground mine in areas where it finds there is no longer danger
from gas or other hazards.
An escape chamber or alternate escape route shall be
maintained within 5,000 feet of the tunnel face or areas being used
to excavate material in an underground mine classified as gassy or
extrahazardous. Workers shall be provided with emergency rescue
equipment and trained in its use.
Records of air flow and air sample tests to assure compliance
with required standards shall be maintained by the employer at the
site of any tunnel or underground mine classified extrahazardous.
Such records shall be made available to any division representative
The main fan line used for ventilation in any tunnel or
underground mine classified extrahazardous shall contain a cutoff
switch capable of halting all machinery underground automatically
should the fan fail or its performance fall below minimum power
needed to maintain a safe atmosphere.
In any tunnel or underground mine classified extrahazardous a
device or devices which automatically and continuously test the
atmosphere for gases or vapors shall be maintained. Such device or
devices shall be placed as near the face or area of operation as
practical, but never more than 50 feet from such point. The division
shall determine if additional monitors are necessary and where they
should be located. This requirement shall apply only to tunnels or
underground mines where excavation of material is by mechanical
All such testing device or devices shall be U.S. Bureau of
Mines approved or acceptable to other authorities recognized by the
division and shall automatically sound an alarm and activate flashing
red signals visible to employees underground whenever the
concentration of gases or vapors reaches or exceeds permissible
levels. Permissible levels may be established lower than the limits
set in division rules, regulations, or general orders whenever a
division inspector considers such action necessary to make the
operation safe for employees.