Criteria for a Recommended Standard: Occupational Exposure to Hot Environments was revised in 1986. The revision takes into account the large amount of new scientific information on working in heat and hot environments. This revision includes updated information on heat-related illnesses, risk factors affecting heat-related illness, physiological responses to heat, effects of clothing on heat exchange, and recommendations for control and prevention. Occupational exposure to heat can result in injuries, disease, death, and reduced productivity. Workers may be at risk for heat stress when exposed to hot environments. Exposure to hot environments and extreme heat can result in illnesses, including heat stroke, heat exhaustion, heat syncope, heat cramps, and heat rashes, or death. Heat also increases the risk of workplace injuries, such as those caused by sweaty palms, fogged-up safety glasses, and dizziness.