Section 43.60. Ventilation

(a) The supply of fresh air to the working chamber shall be sufficient at all times to permit work to be done without danger or discomfort. All air supply lines shall be equipped with check valves and carried as near to the face as practicable. The air shall be analyzed by the contractor as required and a record shall be kept of such analysis.

(b) Each working chamber shall have exhaust valves, with risers extending to the upper part of the chamber if necessary. The exhaust valves shall be operated at such times as may be required and especially after a blast, and men shall not be required to resume work after a blast until the gas and smoke have cleared.