Occupational exposure to heat can result in injuries, disease, reduced productivity, and fatality. To address this hazard, the National Institute for Occupational Safety and Health (NIOSH) has evaluated the scientific data on heat stress and hot environments and has updated its Criteria for a Recommended Standard: Occupational Exposure to Hot Environments document.

The document was last updated in 1986, and in recent years, including during the Deepwater Horizon oil spill response of 2010, questions were raised regarding the need for revision to reflect recent research and findings.
In addition, there is evidence that heat stress is an increasing problem for many workers, particularly those located in densely populated areas closer to the equator where temperatures are expected to rise in relation to the changing climate.

The revision includes:
-Additional information about the physiological changes that result from heat stress;
-Updated information from relevant studies, such as those on caffeine use;
-Evidence to redefine heat stroke and associated symptoms; and
-Updated information on physiological monitoring and personal protective equipment and clothing that can be used to control heat stress.