capacity and power capable of supplying the required ventilation,
and shall maintain a sufficient volume of air, not less per minute
than one hundred and fifty cubic feet for each person, and five
hundred cubic feet for each animal working therein, measured at the
intake, and distributed so as to expel or dilute and render
harmless, explosive, poisonous and noxious gases.


[=Additional requirements where fire-damp is present.=] The owner,
lessee or agent of a mine generating fire-damp, so as to be detected
by a safety lamp, shall, in addition to the foregoing, provide and
maintain not less than fifty cubic feet of air per minute for each
person working therein. (Sec. 923, 924, 952; Penalty, Sec. 976.)


Sec. 923. [=Ventilating appliances.=] In each mine, the doors used
in assisting or directing the ventilation thereof, shall be hung so
that they will close themselves, and shall be kept closed except
while persons or cars are passing through same. Each door, not
operated automatically, through which cars are required to pass,
shall have an attendant, whose first duty shall be to open it for
transportation, and prevent it from standing open longer than
necessary for cars to pass through, and, persons in charge of cars
passing through automatic doors shall be required to keep a close
watch over such doors, and if any such door fails to close, they
shall promptly close same and report such fact to the mine foreman.
This shall not prevent the attendant from performing other duties,
provided the door is not kept open longer than is necessary for cars
to pass through. Where necessary, a refuge place shall be provided
at each door for the safety of the attendant. (Sec. 943, 958;