Oil and Gas Occupational Safety and Health Regulations

12.1 In this Part, confined space means a storage tank, process vessel, ballast tank or other enclosure not designed or intended for human occupancy, except for the purpose of performing work,

• (a) that has poor ventilation;

• (b) in which there may be an oxygen deficient atmosphere; or

• (c) in which there may be an airborne hazardous substance. (espace clos)