Oil and Gas Occupational Safety and Health Regulations

11.7 Every ventilation system used to control the concentration of an airborne hazardous substance shall be so designed, constructed and installed that

• (a) if the substance is a chemical agent, the concentration of the chemical agent does not exceed the limits prescribed in sections 11.23 and 11.24; and

• (b) if the substance is not a chemical agent, the concentration of the substance is not hazardous to the safety or health of employees.