Safe Working Practices Regulations (C.R.C., c. 1467)

22 (1) Every enclosed working area in which equipment powered by an internal combustion engine is used shall be ventilated to ensure that the carbon monoxide concentration in the atmosphere of the working area does not exceed 50 parts per million.

(2) No person shall operate equipment powered by an internal combustion engine in an enclosed working area unless there is at least one other person in attendance at the entrance to that working area.