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  • Canaria Technologies

Working in Outdoor and Indoor Heat Environments

According to Occupational Safety and Health Administration(OSHA), Millions of workers are exposed to heat in their workplaces. Although illness from exposure to heat is preventable, every year, thousands become sick from occupational heat exposure, and some cases are fatal. Most outdoor fatalities, 50% to 70%, occur in the first few days of working in warm or hot environments because the body needs to build a tolerance to the heat gradually over time. The process of building tolerance is called heat acclimatization. Lack of acclimatization represents a major risk factor for fatal outcomes.

Occupational risk factors for heat illness include heavy physical activity, warm or hot environmental conditions, lack of acclimatization, and wearing clothing that holds in body heat. (See also, personal risk factors, below.)

Hazardous heat exposure can occur indoors or outdoors, and can occur during any season if the conditions are right, not only during heat waves. The following is a list of some industries where workers have suffered heat-related illnesses.




Bakeries, kitchens, laundries (sources with indoor heat-generating appliances)

Construction - especially, road, roofing, and other outdoor work

Electrical utilities (particularly boiler rooms)

Construction - roofing work

Fire Service


Iron and steel mills and foundries

Mail and package delivery

Manufacturing with hot local heat sources, like furnaces (e.g. paper products or concrete)

Oil and gas well operations



Heat-related illnesses can be prevented. Prevention requires employers and workers to recognize heat hazards. Management should commit to:

  • Take extra precautions to protect new workers.

  • Train supervisors and workers to control and recognize heat hazards.

  • Determine, for each worker throughout each workday, whether total heat stress is too high, both from the conditions of that day and recognizing carryover effect possibilities.

  • Implement engineering and administrative controls to reduce heat stress.

  • Provide sufficient rest, shade, and fluids.

For more information on preventing heat stress, leave a message on this site.


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