We’re approaching 40°C (with humidity) outside today.  Heat stress is a serious issue in the early months of summer in Ontario—and preventing heat stress-related illness in the workplace becomes critical.  The Ministry of Labour defines the legal requirements under the Occupational Health & Safety Act as:

“Legal Requirements:

Employers have a duty under section 25(2)(h) of the Occupational Health and Safety Act to take every precaution reasonable in the circumstances for the protection of a worker. This includes developing hot environment policies and procedures to protect workers in hot environments due to hot processes or hot weather.

For compliance purposes, the Ministry of Labour recommends the Threshold Limit Values (TLVs) for Heat Stress and Heat Strain published by the American Conference of Governmental Industrial Hygienists (ACGIH). These values are based on preventing unacclimatized workers’ core body temperatures from rising above 38°C. “

Heat exposure may occur in many workplaces.  Significant sources of heat can be found in workplaces such as foundries, smelters, chemical plants, bakeries and commercial kitchens.  For outdoor workers, direct sunlight is usually the main source of heat.  In mines, especially in deep mines, geothermal gradients and equipment contribute to heat exposure.  Check out the Ministry of Labour’s resources for controlling and managing heat stress here.