§ 33.174. Ventilation.

 (a)  General requirement. The owner or developer of each mine shall provide and maintain an adequate supply of pure air in the mine as provided in subsection (b). When it becomes necessary to install means of mechanical ventilation, these means for providing pure air shall be approved before they are operated.

 (b)  Quantity of air. The minimum quantity of air supplied to any occupied or enclosed space in a developed area shall be 20 cubic feet of outside air per minute per person.

 (c)  Air movement. There shall be a positive and continuous movement of air through all passageways used for human or vehicular travel.

 (d)  Carbon monoxide. The operator shall be responsible for insuring that carbon monoxide in excess of the maximum allowable concentrations is not present in a developed area.