Heat stress levels for outdoor labor can be measured several different ways, but one of the best options is to use the Wet Bulb Globe Temperature measurement. WBGT takes all four of the following environmental factors into account to determine heat stress levels on outdoor workers in direct sunlight:

  • Air temperature
  • Humidity
  • Radiant heat
  • Wind

Compare WBGT to the heat index which only takes into account the humidity and air temperature to determine how hot conditions feel while the body is at rest and in the shade.

Fill in the following form to determine whether a worker’s heat stress is above recommended limits. Please read OSHA’s Heat Hazard Recognition page for more information about WBGT, workload, acclimatization status, and clothing.

Degrees Fahrenheit


What’s next?

Using the information from this calculator effectively requires being familiar with what heat stress looks like.

First, recognize those who are at a higher risk for heat related illnesses such as those who are 65 or older or those with existing health conditions. Next, take into account the environment and the workload required of employees, whether that be at a bakery, in the firefighting industry, or places such as factories. Lastly, learn to recognize the symptoms of heat stress, how to treat it, and most importantly, how to prevent heat stress from happening in the first place.

Training employees in a way that promotes awareness about the dangers of working outside in the heat is critical for illness prevention and emergency preparedness.

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