Warmer weather is coming our way. It is time to review your company policies and procedures on heat stress.

Overexposure to heat can stress the body’s cooling system. When the heat is combined with other stressors such as hard physical work, loss of fluids, fatigue or some medical conditions, it may lead to heat-related illness, disability and even death.

Heat Stress- the overloading of the body’s cooling system- can happen to anybody even if you are young and fit. In Ontario heat stress is usually a concern during the summer. This is especially true early in the season, when people are not used to the heat.

Some industries or operations involving high air temperatures, radiant heat sources from molten materials, high humidity, and direct physical contact with hot objects or strenuous physical activities have a potential for heat stress all year round. These include iron and steel foundries, brick firing and ceramic plants, glass products facilities, rubber product factories, bakeries, laundries, smelters and steam tunnels.

How We Cope With Heat
Normal body temperature is 37º Celsius (98.6º Fahrenheit). This temperature must remain constant for the body to work well. When the body heat increases, the body removes heat through the skin. Blood vessels near the skin open up to bring more warm blood to the surface. Heat then escapes and the body cools. When the air temperature is high, the main source of cooling is the evaporation of sweat. However, when the humidity is high, sweat does not evaporate as quickly and has little or no cooling effect. The hotter or more humid the environment, the harder your body must work to get rid of its excess heat.

If the air is moving (for example, from fans) and it is cooler then your body, it is easier for your body to pass heat to the environment.

Workers over the age of 40 should be more careful because of a reduced ability to sweat.

The 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.