Heat stress guidelines

The Ministry of Labour (MOL) has developed guidelines to deal with heat stress and assist employers in meeting their obligations under the Occupational Health and Safety Act (OHSA). The policy is intended to help employers, supervisors and workers understand heat stress, in order to develop and implement workplace policies to prevent heat stress related illnesses. This stems from Section 25(2)(h) of OHSA which states that every precaution reasonable should be taken for the protection of a worker.

Heat stress refers to an increase in the body’s core temperature. This could be due to several variables, including air temperature, humidity, radiant heat and the humidex. If a person is experiencing heat stress, a series of health complications can develop, including: heat rash, heat cramps, heat exhaustion, or heat stroke. When the body’s temperature rises above 38 degrees Celsius, the brain starts to overheat, leading to a shutdown of your body’s cooling system.

Heat Stress Plans, (or Hot Weather Action Plans), deal with hot/humid weather and should be in place, at a minimum, from May 1 to September 30 of each year as per the MOL’s heat stress guidelines. Principals or supervisors should review the plan with staff, are responsible to ensure that water is available for all employees at every work location, and should have the temperature and humidity measured regularly.

The plan should be activated when heat waves occur with three or more consecutive days of temperatures at 32 degrees Celsius or higher, when the humidex reaches or exceeds 35 degrees Celsius, when there is a smog alert combined with higher temperatures, and when there is an Environment Canada Humidex Advisory.

To keep work locations cool, the supervisor and staff are encouraged to keep lights and computers turned off when possible, use fans, keep windows and doors open, and if there are air-conditioned areas in the building, rotate people into those rooms throughout the day.

The Provincial Working Group on Health and Safety has developed a heat stress template to assist school boards in implementing best practices. It should be posted on the Ministry of Education website soon.