On Board Trains Occupational Health and Safety Regulations

8.9 Where a steel or aluminum self-contained breathing apparatus cylinder has a dent deeper than 1.5 mm and less than 50 mm in major diameter or shows evidence of deep isolated pitting, cracks or splits, the cylinder shall be removed from service until it has been shown to be safe for use by means of a hydrostatic test at a pressure equal to one and one-half times the maximum allowable working pressure.