Regulations Made Under Part II of the Canada Labour Code Respecting Occupational Safety and Health of Employees Employed on or in Connection with Exploration or Drilling for, or the Production, Conservation, Processing or Transportation of, Oil or Gas in Canada Lands, as Defined in the Canada Oil and Gas Act

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)