It shall be the duty of every person constructing any underground work within the corporate limits of the city to maintain, through any shaft, conduit, or underground work where men or animals are employed, currents of air sufficient for the health and safety of all the men and animals employed therein, and such ventilation shall be produced by fans or other artificial means.
The quantity of air to be kept in circulation and passage at a given point shall be not less than 75 cubic feet per minute for each person, and not less than 300 cubic feet per minute for each animal, measured at the foot of the downcast; and this amount may be increased in the discretion of the inspector whenever in his judgment unusual conditions make a stronger current necessary.
(Prior code § 180-2)