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A Guide to Managing Heat Stress
It’s not your imagination. It IS hotter outside. In fact, summer temperatures over the last decade have been the hottest on record.
Since 1983, U.S. heat waves have caused more deaths than hurricanes and floods combined.
Heat stress occurs when the body cannot get rid of excess heat. The body's core temperature rises, and the heart rate increases. As the body continues to store heat, the person begins to lose concentration and has difficulty focusing on a task. He or she may become irritable or sick, and often loses the desire to drink. The next stage is fainting and possibly death if the person is not cooled down.
Factors that contribute to heat stress are high temperatures, radiant heat exposure, high humidity, direct physical contact with hot objects, and strenuous physical activities.
The Occupational Health and Safety Act mandates that employers provide their workers a place of employment that is free from recognized hazards likely to cause death or serious physical harm. Below you’ll find practices and techniques that can eliminate the dangers of heat stress from your work environment.
Heat stress prevention techniques fall into three general categories, based on their effectiveness. The first category is engineering controls that limit the environmental heat load and improve the rate of heat elimination from the body. The second category involves changes to work practices and administrative controls that reduce workplace heat stress. The third category includes training and personal protective equipment (PPE) to limit the heat stress risk.
Engineering controls modify the rate of heat exchange between workers and their environment. Air temperature and velocity are the main factors that affect heat lost or gained in the body. Heat loss occurs when the ambient air temperature is lower than skin temperature (approximately 95°F). Under these conditions, increasing air velocity with fans can increase the rate of heat loss. If the ambient air temperature is greater than 95°F, increasing ambient air velocity will cause the body to gain heat.
To reduce the effects of radiative heat, place a reflective screen between the radiant heat source and the worker(s). The type of reflective screen can vary in complexity, from insulated furnace jackets to reflective metal shields or reflective clothing like firefighters wear. Covering the body in normal clothing can also provide some protection from radiant heat sources.
Engineering Control Recommendations:
Reduce the chance of heat stress through work practices that control the rate of body heat generation. This can be achieved by scheduling hot or strenuous work during cooler parts of the day. Workers should also have an opportunity acclimatize to hot conditions.
Frequent rest breaks help limit core heat buildup and allows the body time to dissipate excess heat. Sometimes it may be necessary to use a larger workforce for especially hot jobs to ensure the work-rest schedule can be maintained.
Administrative Practice Recommendations:
Training and PPE
Worker training is a critical aspect of a heat stress prevention program. Program objectives should include:
To reduce heat stress incidents, conduct medical screenings for workers exposed to hot work environments. This will help identify employees with limited heat coping ability due to existing health problems such as heart disease. Other measures such as reflective clothing or personal ice vests can limit heat buildup and extend the time a person can work in a hot environment without undue risk of heat stress.