Canada Occupational Health and Safety Regulations

10.21 (1) Compressed air, gas or steam shall not be used for blowing dust or other substances from structures, machinery or materials where

• (a) there is a risk of any person being directly exposed to the jet or where a fire, explosion, injury or health hazard is likely to result from such use; or

• (b) such use would result in a concentration of an airborne hazardous substance that is in excess of the value referred to in paragraph 10.19(1)(a) or subsection 10.19(1.1) or the limit referred to in subsection 10.20(1) or (2).