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Managing heat stress and working in hot environments

When working in hot environments body temperature may rise, and the body responds by sweating.  As the sweat evaporates it cools the body.  If the process does not work several heat related illnesses may occur.  Water is key to this process; by providing adequate blood volume to transfer heat outward and perspiration to cool the body.

Other factors are as follows:

Heat Related Illnesses

Heat rash


Heat Cramps

Heat Exhaustion

Heat Stroke

Warning: Pregnant women, especially in the first trimester, are at increased risk for birth defects if body temperature is evaluated for extended periods of time.  Consult a physician.

Administrative Controls

Adequate fluid intake

Drink ample fluids throughout the day.

To encourage workers to drink water it should be readily accessible and kept clean and cool.

Acclimatize workers

Acclimatized worker will have increased ability to work in heat and be more resilient to the stress.  The process takes 4-7 days and there is a substantial loss when workers leave the work routine for one week or more and must be reacclimatized. 

Medical evaluation

A physician can help identify high risk groups that are more susceptible to heat stress.  Screen for the following:

Engineering Controls

Fans can be used to increase circulation and increase evaporation of sweat. 

Personal Protective Clothing

Measurement of Heat Stress

Heat stress is measured using the Wet Bulb Globe Thermometer (WBGT).  The ACGIH has TLVs to assist in interpreting these measurements that establish a work rest routine appropriate for the type of work being done.

Evaluation strategy


In a changing work environment, the best approach is good employee education and management controls.

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