On Board Trains Occupational Health and Safety Regulations

7.21.1 Compressed air, gas or steam shall not be used for blowing dust or other substances from structures, machinery or materials if

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

• (b) that use would result in either a concentration of an airborne chemical agent that is in excess of the values referred to in paragraph 7.20(1)(a) or subsection 7.20(1.1) or a concentration of an airborne chemical agent or combination of airborne chemical agents that is in excess of the maximum concentration set out in subsection 7.21(1) or (2).