168. Medical lock.- The employer shall ensure at a construction site of a building or other construction work that,- (a) a suitably constructed medical lock is maintained at tunnelling work where building workers are employed in a working chamber at a pressure exceeding one bar; (b) where more than one hundred building workers are employed in a compressed air working environment exceeding one bar at tunnelling work, one medical-lock is provided for every one hundred building workers or part thereof and such medical lock is situated as near as possible to the main lock used at such tunnelling work. | 
