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.