Added by Stats. 1972, Ch. 1430.
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.
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