The temperature can feel even hotter than the Heat Index suggests.

Are you doing enough to protect workers from heat stress?

Heat illnesses such as heat stroke don’t arise just from working in certain temperatures. The humidity counts, too, as does how much direct sun the person is in, how breathable their clothes are, how acclimated to the heat they are, and of course, how hard they are working.

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OSHA recently analyzed 25 cases of heat-related illness in outdoor workers — including 14 deaths — and concluded that current guidance around exposure limits to heat stress may not protect workers well enough. That guidance, from the National Institute for Occupational Safety and Health (NIOSH), states that unless certain risk factors are present, such as direct sun, lack of wind, nonbreathable clothing and a strenuous workload, a Heat Index of less than 91°F is associated with “lower” risk of heat-related illness.

Based on its analysis, however, OSHA now concludes that a Heat Index screening threshold of 85°F “could identify potentially hazardous levels of workplace environmental heat. Protective measures should be implemented whenever the exposure limits are exceeded.” Those measures could include scheduling more breaks or lightening the workload, for example.

According to the National Weather Service, the Heat Index takes into account temperature and humidity only — and it’s measured in the shade. A more accurate measure of how the heat feels is the WetBulb Globe Temperature (WBGT), which also takes into account the wind speed, the angle of the sun and any cloud cover. OSHA recommends using the Heat Index as a guide to the heat stress workers face only when the WBGT is not available.  

Proper planning and controls are key to protecting workers from heat stress and heat illness. OSHA suggests that a heat-related illness prevention program include a work schedule for newly hired workers and long-term workers who aren’t yet acclimatized to the heat, training on recognizing symptoms of heat-related illnesses and how to provide first aid, engineering controls, such as structures that provide shade and reflective shields to block radiant heat, and administrative controls, such as scheduling work earlier in the day and using relief workers when needed. 

Marianne Wait is an editor and writer who creates content for Fortune 500 brands. 

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