Heat rules in Canada: British Columbia's limits and Ontario's guidance
What WorkSafeBC, the BC Occupational Health and Safety Regulation, the Ontario Ministry of Labour and the Canadian Centre for Occupational Health and Safety say about heat at work: screening limits, assessment, water and removal from heat.
Checked against the sources at the bottom of this page on October 8, 2026. Rules, fees and pay change: the source has the last word.
This page reports what the official source says. It is not legal advice: ask the office named here. Canadian workplace safety is provincial, and this page covers only the two provinces whose pages were read on October 8, 2026: British Columbia and Ontario. Other provinces and the federal sector are not covered here, and a missing province is not a statement that it has no rule. The comparison of every place is on the heat rules overview.
British Columbia: a regulation with a limit
Division 4 of Part 7 of the BC Occupational Health and Safety Regulation covers heat exposure in sections 7.26 to 7.32. Its definition of an unacclimatized worker is someone not used to hot environments, or out of one for seven consecutive days. Section 7.27 says the heat rules apply where a worker may face heat stress, where core body temperature could exceed 38 degrees Celsius, or where conditions exceed the screening criteria for unacclimatized workers.
| Section | What the regulation says |
|---|---|
| 7.28 Exposure limits | Workers are not to be exposed to conditions above the screening criteria of the American Conference of Governmental Industrial Hygienists (ACGIH), adjusted for clothing as the ACGIH standard sets out |
| 7.29 Assessment and plan | The employer carries out a heat stress assessment by a method the Board accepts, and develops and implements a heat stress exposure control plan |
| 7.30 Controls | Engineering controls come first to bring exposure under the screening levels. If those are not practicable, administrative controls such as an accepted work-rest cycle, or equally effective personal protective equipment |
| 7.31 Water | An adequate supply of cool potable water close to the work area |
| 7.32 Removal and treatment | A worker who shows signs or reports symptoms of heat stress or strain is removed from the hot environment and treated by a first aid attendant if available, or by a physician |
The regulation text read does not set training or acclimatization programs in these sections. The ACGIH criteria are in WBGT degrees Celsius, the wet bulb globe temperature, which the Canadian Centre for Occupational Health and Safety (CCOHS) explains combines air temperature, humidity, air movement and radiant heat.
WorkSafeBC's heat stress page
WorkSafeBC's page on heat stress says all employers are responsible for managing the risk. It names four ways to judge exposure: the humidex method, the WBGT method, body temperature and heart rate. It says employers should have a heat stress exposure control plan in place before hot weather begins, and should begin monitoring conditions as temperatures approach 23 to 25 degrees Celsius. In the page's words these temperatures are not exposure limits. They are an early indicator of when to begin measures. The page says heat stress can occur at lower temperatures when workers wear protective clothing that stops the body cooling itself. Its control list runs from cancelling or postponing work, through shade structures and air-conditioned vehicles as cooling stations, to rescheduling hard tasks away from the hottest hours, work-rest cycles, cool water and a buddy system. It says protective equipment is not an effective heat control in most cases. Its construction examples include evaporative neck shades and crown coolers worn under hard hats.
Ontario: guidance under a general duty
The Ontario Ministry of Labour page on managing heat stress says the Occupational Health and Safety Act requires employers to take "every reasonable precaution in the circumstances" to protect workers, which may include protection from heat stress. The page sets no numeric workplace exposure limit. It describes engineering controls first, then planning measures such as more and longer rest breaks, scheduling strenuous work for cooler hours, cool drinking water, a buddy system and an emergency response plan. It says new workers can build tolerance by increasing hot-environment time gradually over one to two weeks, and that workers returning after 9 or more days away need to readjust. For a simplified hot weather plan covering May 1 to September 30 it lists these triggers: a humidex of 35 or more on site, an air temperature over 30 degrees Celsius with a humidex of 40, a heat wave of 32 degrees Celsius or more forecast for three or more days, or a smog alert. For workplaces with process heat the page points to the ACGIH values, which are sold for a fee.
CCOHS adds that the ACGIH values have been formally adopted as occupational exposure limits in some jurisdictions and used as guidelines in others.
Sources
- WorkSafeBC, Heat stress, read October 8, 2026
- WorkSafeBC, Occupational Health and Safety Regulation Part 7 (Noise, Vibration, Radiation and Temperature), Division 4 Thermal Exposure, read October 8, 2026
- Ontario Ministry of Labour, Managing heat stress at work, read October 8, 2026
- Canadian Centre for Occupational Health and Safety, Hot environments: assessment and control measures, read October 8, 2026