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  • Writer's pictureTom Petersen

OSHA and Reducing Heat Stress in Working Environments

As summer approaches, heat stress becomes an increasingly important factor in ensuring safe working conditions. Heat stress is any illness caused by high temperatures and it can pose a significant danger in industrial working environments.

Resources from OSHA:

Under the General Duty Clause, Section 5(a)(1) of the Occupational Safety and Health Act of 1970, employers are required to provide their employees with a place of employment that "is free from recognized hazards that are causing or likely to cause death or serious harm to employees." The courts have interpreted OSHA's general duty clause to mean that an employer has a legal obligation to provide a workplace free of conditions or activities that either the employer or industry recognizes as hazardous and that cause, or are likely to cause, death or serious physical harm to employees when there is a feasible method to abate the hazard. This includes heat-related hazards that are likely to cause death or serious bodily harm. 

Environmental heat is more than just temperature. Four factors contribute to heat stress in workers:

  1. Air temperature.

  2. Humidity. High relative humidity makes it difficult for the body to cool itself through sweating.

  3. Radiant heat from sunlight or artificial heat sources such as furnaces.

  4. Air movement. In most situations, wind helps workers cool off.

An environmental heat assessment should account for all of these factors. OSHA recommends the use of wet bulb globe temperature (WBGT) monitor to measure workplace environmental heat.

WBGT devices contain three different thermometers:

  • A dry bulb thermometer to measure the ambient air temperature.

  • A natural wet bulb thermometer to measure the potential for evaporative cooling.

  • A black globe thermometer to measure radiant heat.

Heat Index is another common way to measure heat stress. It is measured in the shade and combines air temperature and relative humidity to represent how hot the conditions feel at rest.

But the Heat Index does not measure worksite heat as accurately as WBGT. Employers should not rely on Heat Index alone for the most accurate hazard assessment. Some employers may find the Heat Index helpful as part of a more comprehensive workplace hazard assessment.

Ways to beat the heat:

  • Get a ventilation assessment to maximize your airflow.

  • Spot coolers (portable air conditioners) are effective in certain settings.

  • Cooling vests for your workers.

If you are interested in getting a ventilation assessment or have any questions relating to ventilation, please contact EES at or call 215-704-1506.

For more information on government guidelines and recommendations:


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