Canada Occupational Health and Safety Regulations

10.20 (1) Subject to subsection (2), the concentration of an airborne chemical agent or combination of airborne chemical agents in the work place shall be less than 50 per cent of the lower explosive limit of the chemical agent or combination of chemical agents.

(2) Where a source of ignition may ignite an airborne chemical agent or combination of airborne chemical agents in the work place, the maximum concentration of the chemical agent or of the combination of chemical agents shall be 10 per cent of the lower explosive limit of the chemical agent or combination of chemical agents.

(3) Subsection (2) does not apply in respect of concentrations of methane gas in the underground portion of a coal mine.