Heat Exposure

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With summer fast approaching, one safety & health concern employers often overlook is exposure to heat. Currently OSHA does not comprehensively address the issue of heat exposure. The following are a few guidelines for what are safe levels of heat for employees to be exposed to and how to protect employees.

This chart was developed to reflect what temperature “it feels like” in shady conditions with a light wind. Full sun can increase the apparent temperature by up to 15°F/8°. Strong winds can be extremely dangerous when coupled with dry, hot air. The figures shown on this chart were developed by the National Oceanic & Atmospheric Association.

For example, assuming employees are working in a shady environment with an air temperature of 90°F/35°C with a relative humidity of 70%, the workers would feel as though they are being exposed to 106°F/41°C temperatures, which is a high risk level that requires high levels of precaution to protect workers.

If these same conditions were experienced in a full sun environment the workers could feel like they are exposed up to 121°F/49°C, which has an extreme level of risk and requires aggressive protective measures to keep employees safe.

If high wind were added to this equation the danger level would increase even greater.

Safe precautions can include things such as providing a cooler of sports drinks or water, adjusting the work/rest cycle, or providing employee cooling equipment.

The following table, developed by the American Conference of Governmental Industrial Hygienists (ACGIH), is designed to give employers an idea of what temperatures are considered safe depending on how strenuous the work activity is and the time worked in the work/rest cycle.

For example, if employees are performing work that is moderately strenuous in an environment that feels 83°F/28°C they are safe to work about 75-100% of every hour in that environment. If that work load increases to very heavy strain, employees should not work more than 25-50% of each hour without rest to cool themselves and rehydrate.

*Unless specific citations are shown, all answers are based on interpretations provided by authorized officials. As such, all information is deemed reliable, but not guaranteed.