164. Quality and quantity of air.- The employer shall ensure at a construction site of a building or other construction work that,- (a) every working chamber at an excavation or tunnelling work where compressed air is used, the supply of such air is maintained not less than zero point three cubic meters per minute per person working therein; (b) a reserve supply of compressed air is made available at all times for man-locks and medical locks used at a tunnelling work; (c) the air supplied in a compressed air environment at a tunnelling work is as far as practicable free from odour and other contaminants, namely, dust, fumes and other toxic substances. | 
