Managing Heat Stress and Working In Hot Environments

Heat and hot environments can pose multiple safety and health issues. Know what they are, how to treat them and how to prevent them.

Information provided by ACPA and Travelers Insurance

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:

  • Humidity which may inhibit evaporation of sweat.
  • Inadequate water intake.
  • High ambient air temperature or radiant heat from blast furnaces or sunshine.
  • Various protective clothing that may add to the heat load of the employee.

Heat Related Illnesses

Heat Rash

Sweat duct becomes blocked and sweat accumulates in the gland. Heat rash is uncomfortable and can lead to more serious disorders due to lack of sweating.

First aid
Apply drying lotion and powder.

Regular bathing keeps skin dry and clean.

Common among workers not acclimated to working in hot environments. Caused by blood pooling in lower extremities.

First aid
Remove employee to cooler area and lay down briefly, recovery is prompt and complete.

Proper acclimatization and avoid standing erect for extended periods of time; move around.

Heat Cramps

Painful spasms of the muscles used during or after work; caused by excessive loss of salt from sweating.

First aid
Consumption of electrolyte replacement beverage.

Adequate salt intake during meals. No need for salt tablets, normal diet has ample salt. Begin drinking replenishing fluids one to two hours before beginning work in hot environment.

Heat Exhaustion
Fatigue, nausea, headache, rapid heart rate and moist clammy skin. Can progress to heat stroke.

First aid
Rest in cool area and drink fluids. Severe cases may require intravenous fluids.

Acclimatization of worker and drinking ample water during work.

Heat Stroke
Elevated body temperature, unconsciousness or convulsions, lack of sweating and possible vomiting and diarrhea.

First aid
A medical emergency that requires professional medical treatment. Move patient to cool area, bath in cool water or cover in cool water soaked towels. Remove outer clothing and treat for shock. Give no oral liquid if convulsing or unconscious.

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.

  • BEST: plain cool (50-60 degrees F) water.
  • AVOID: alcohol, caffeinated beverages such as tea and coffee which are diuretics, and excessive carbohydrates such as soda and fruit juice which can inhibit water uptake.
  • Increase rest periods throughout the day.
  • Job rotation for high exposure jobs.
  • Schedule hot work for cooler periods in the day.
  • Employee and supervisor training on heat related issues.

To encourage workers to drink water is 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 to 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:

  • Physically fit – poor muscle conditioning and obesity limit heat dissipation.
  • Medications taken by employees may adversely affect thermoregulation. Employees should notify their supervisor of medications they are taking.

Engineering Controls

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

  • If air temperature is greater than 95 degrees F then fans should not be used, they will actually heat worker. Average skin temperature is 95 degrees F. In this case the air temperature must be reduces with auxiliary cooling methods.
  • Shields and barriers to protect worker from direct radiant heat source.

Personal Protective Clothing

  • Air cooled or water cooled garments.
  • Air supplied hoods and suits can be adapted to provide cooled air.
  • Wetted head bands and other overgarments.

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

  • Identify the work type
  • Determine current work/rest regimen
  • Collect WBGT data
  • Use WBGT index to evaluate
  • Make necessary adjustments


  • Educate
  • Identify workers at risk
  • Monitor environment and make adjustments
  • Provide PPE, water, rest and first aid as required

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


National Safety Council. Fundamentals of Industrial Hygiene – Third Edition, 1988

AIHA Press. Occupational Environment 0 Its Evaluation of Control – Chapter 25 Thermal Standards and Measurement Techniques, 1997

American Conference of Governmental Industrial Hygienists. "Threshold Limit Value – Heat Stress," 2001

The information provided in this document is intended for use as a guideline and is not intended as, nor does it constitute, legal or professional advice. Travelers does not warrant that adherence to, or compliance with, any recommendations, best practices, checklists, or guidelines will result in a particular outcome. In no event will Travelers or any of its subsidiaries or affiliates be liable in tort or in contract to anyone who has access to or uses this information. Travelers does not warrant that the information in this document constitutes a complete and finite list of each and every item or procedure related to the topics or issues referenced herein. Furthermore, federal, state or local laws, regulations, standards or codes may change from time to time and the read should always refer to the most current requirements. This material does not amend, or otherwise affect, the provisions or coverages of any insurance policy or bond issued by Travelers, nor is it a representation that coverage does or does not exist for any particular claim or loss under any such policy or bond. Coverage depends on the facts and circumstances involved in the claim or loss, all applicable policy or bond provisions, and any applicable law.

© 2008 The Travelers Companies, Inc. All rights reserved.
Doc#: 514