Protecting Workers in Hot Environments

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Many workers spend some part of their working day in a hot environment.  Workers in foundries, laundries, construction projects, canneries and bakeries ‑ to name a few industries ‑ often face hot conditions that pose special hazards to safety and health.


Four environmental factors affect the amount of stress a worker faces in a hot work area ‑temperature, humidity, radiant heat (such as from the sun or a furnace) and air velocity.  Perhaps most important to the level of stress an individual faces are personal characteristics such as age, weight, fitness, medical condition and acclimatization (physical conditioning / adjustment) to the heat.

The body reacts to high external temperature by circulating blood to the skin, which increases skin temperature and allows the body to give off its excess heat through the skin.  However, if the muscles are being used for physical labor, less blood is available to flow to the skin and release the heat.

Sweating is another means the body uses to maintain a stable internal body temperature in the face of heat.  However, sweating is effective only if the humidity level is low enough to permit evaporation and if the fluids and salts lost are adequately replaced.

Of course there are many steps a person might choose to take to reduce the risk of heat stress, such as moving to a cooler place, reducing the work pace or load, or removing or loosening some clothing.

If the body cannot dispose of excess heat, it will store it.  When this happens, the body’s core temperature rises and the heart rate increases.  As the body continues to store heat, the individual begins to lose concentration and has difficulty focusing on a task, may become irritable or sick and often loses the desire to drink.  The next stage is most often fainting and then possible death if the person is not removed from the heat stress.



Most heat‑related health problems can be prevented or the risk of developing them reduced.  The following are some basic precautions that should lessen heat stress.


A 15‑page booklet, Working in Hot Environments, is available free from National Institute for Occupational Safety and Health Publications, 4676 Columbia Parkway, Cincinnati, Ohio 45226; telephone 1-800-356-4674 or contact the IBT Safety and Health Department.