Canada Occupational Health and Safety Regulations

11.10 (1) Where ventilation equipment is used to maintain the concentration of a chemical agent or combination of chemical agents in a confined space at or below the concentration referred to in subparagraph 11.4(1)(a)(i), or to maintain the percentage of oxygen in the air of a confined space within the limits referred to in subparagraph 11.4(1)(a)(iii), the employer shall not grant access to the confined space to any person unless

• (a) the ventilation equipment is

  • (i) equipped with an alarm that will, if the equipment fails, be activated automatically and be audible or visible to every person in the confined space, or

  • (ii) monitored by an employee who is in constant attendance at the equipment and who is in communication with the person or persons in the confined space; and

• (b) in the event of failure of the ventilation equipment, sufficient time will be available for the person to escape from the confined space before

  • (i) the concentration of the chemical agent or combination of chemical agents in the confined space exceeds the concentrations referred to in subparagraph 11.4(1)(a)(i), or

  • (ii) the percentage of oxygen in the air ceases to remain within the limits referred to in subparagraph 11.4(1)(a)(iii).

(2) If the ventilation equipment fails to operate properly, the employee referred to in subparagraph (1)(a)(ii) shall immediately inform the person or persons in the confined space of the failure of the equipment.