Ordinarily, the body remains at a fairly constant temperature of 98.6F. It is important to maintain this body temperature. Since there is a continuous heat gain from internal body processes, there must be a continuous loss to maintain body heat balance. Excess heat must be absorbed by the surrounding air or lost by radiation. As the temperature and humidity of the

environment vary, the body automatically regulates the amount of heat that it gives off. However, the body's ability to adjust to varying environmental conditions is limited. Furthermore, although the body may adjust to a certain (limited) range of atmospheric conditions, it does so with a distinct feeling of discomfort. The discussion that follows will help you understand how atmospheric conditions affect the body's ability to maintain a heat balance.

Body Heat Gains

The body gains heat by radiation, by convection, by conduction, and as a by-product of physiological processes that take place within the body.

The heat gain by radiation comes from our surroundings. However, heat always travels from areas of higher temperature to areas of lower temperature. Therefore, the body receives heat from those surroundings that have a temperature higher than body surface temperature. The greatest source of heat radiation is the sun. Some sources of indoor heat radiation are heating devices, operating machinery, and hot steam piping.

The heat gain by convection comes only from currents of heated air. Such currents of air may come from a galley stove or an engine.

The heat gain by conduction comes from objects with which the body comes in contact.

Most bodes comes from within the body itself. Heat is produced continuously inside the body by the oxidation of foodstuffs and other chemical processes, friction and tension within the muscle tissues, and other causes.

Body Heat Losses

There are two types of body heat losses-loss of sensible heat and loss of latent heat. Sensible heat is given off' by radiation, convection, and conduction. Latent heat is given off in the breath and by evaporation of perspiration.