Canada Occupational Health and Safety Regulations

10.21 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) that use would result in a concentration of an airborne chemical agent that exceeds the values 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).