Editing Hyperthermia (section)

==Prevention==
When ambient temperature is excessive, humans and many other animals cool themselves below ambient by [[evaporative cooling]] of [[sweat]] (or other aqueous liquid; [[saliva]] in dogs, for example); this helps prevent potentially fatal hyperthermia. The effectiveness of evaporative cooling depends upon [[humidity]]. [[Wet-bulb temperature#Wet-bulb temperature and health|Wet-bulb temperature]], which takes humidity into account, or more complex calculated quantities such as [[wet-bulb globe temperature]] (WBGT), which also takes [[solar radiation]] into account, give useful indications of the degree of heat stress and are used by several agencies as the basis for heat-stress prevention guidelines. (Wet-bulb temperature is essentially the lowest skin temperature attainable by evaporative cooling at a given ambient temperature and humidity.)

A sustained wet-bulb temperature exceeding {{convert|35|C|F}} is likely to be fatal even to fit and healthy people unclothed in the shade next to a fan; at this temperature, environmental heat gain instead of loss occurs. {{As of|2012}}, wet-bulb temperatures only very rarely exceeded {{convert|30|C|F}} anywhere, although significant [[global warming]] may change this.<ref>{{cite journal |title=Thermogeddon: Too hot for humans |first=Hazel |last=Muir |journal=New Scientist |volume=208 |issue=2783 |pages=36–39 |doi=10.1016/S0262-4079(10)62649-8 |date=23 October 2010 |bibcode=2010NewSc.208...36M }}<!--|access-date=2 August 2015--></ref><ref>{{Cite web|last=Madge|first=Grahame|date=2021-11-09|title=One billion face heat-stress risk from 2°C rise|url=https://www.metoffice.gov.uk/about-us/press-office/news/weather-and-climate/2021/2c-rise-to-put-one-in-eight-of-global-population-at-heat-stress-risk|access-date=2021-11-10|website=Met Office|language=en}}</ref>

In cases of heat stress caused by physical exertion, hot environments, or protective equipment, prevention or mitigation by frequent rest breaks, careful hydration, and monitoring body temperature should be attempted.<ref>{{cite web|title=NIOSH Workplace Safety and Health Topics: Heat Stress|url=https://www.cdc.gov/niosh/topics/heatstress/|publisher=National Institute for Occupational Safety and Health|access-date=21 March 2014}}</ref> However, in situations demanding one is exposed to a hot environment for a prolonged period or must wear protective equipment, a personal cooling system is required as a matter of health and safety. There are a variety of active or passive personal cooling systems;<ref name=MicroclimateCooling/> these can be categorized by their power sources and whether they are person- or vehicle-mounted.

Because of the broad variety of operating conditions, these devices must meet specific requirements concerning their rate and duration of cooling, their power source, and their adherence to health and safety regulations. Among other criteria are the user's need for physical mobility and autonomy. For example, active-liquid systems operate by chilling water and circulating it through a garment; the skin surface area is thereby cooled through conduction. This type of system has proven successful in certain military, law enforcement, and industrial applications. Bomb-disposal technicians wearing special suits to protect against improvised explosive devices (IEDs) use a small, ice-based chiller unit that is strapped to one leg; a liquid-circulating garment, usually a vest, is worn over the torso to maintain a safe core body temperature. By contrast, soldiers traveling in combat vehicles can face microclimate temperatures in excess of {{cvt|65|C}} and require a multiple-user, vehicle-powered cooling system with rapid connection capabilities. Requirements for hazmat teams, the medical community, and workers in heavy industry vary further.