Operator/crew comfort inside a combat vehicle has not had the attention and priority it truly deserves. Inside combat vehicles accommodation is often cramped and surfaces are hard and unfriendly that could easily cause injury to the occupant. Adding excessive heat to this scenario only increases the chance for failure to perform, injury or possible loss of life. The field manual 90-30, Desert Operations, states, “highest known ambient temperature recorded in a desert was 136deg F, lower temperatures than this produced internal tank temperatures approaching 160 deg F in the Sahara Desert during the Second World War”. It is a fact that a weapon is only as good as its operator. An alert operator at his or her peak efficiency tends to perform better. The effect of heat on a combat vehicle crew can be considered a continuum ranging from discomfort to heat casualty (exhaustion and heat stroke). What may not be readily apparent is the physical and mental degradation that can occur before symptoms become apparent enough to cause perceptible heat illness.
Research has shown that human tolerance, alertness and efficiency drops significantly when operating in excessively hot environments. For example 120 Deg F, Dry Bulb, and 70% humidity is marginally tolerable for ½ hour for a fully clothes sitting person (See Fig 1, Exposure limits for sitting clothed subjects). Main objectives are To prevent heat energy from entering the vehicle cabin, and to remove excess heat from the interior, hence maintaining a relatively comfortable environment for long periods of confinement during military operations.