a. Environmental Conditions Affecting Body Heat and the Body's
Adjustments to Heat. The conditions in the environment which influence the heat of
the body and its adjustments are:
Temperature of the air.
Temperature of the surrounding objects.
Vapor pressure of the water in the air (relative humidity).
Type and amount of clothing worn.
b. Ways the Body Gains and Loses Heat. Three ways in which the body
gains and looses heat are conduction, radiation, and evaporation.
c. Heat Loss by Conduction. Heat loss by conduction to the air occurs when
the air temperature is below body temperature. Conversely, heat gain by conduction
occurs when air temperature exceeds that of the body.
d. Heat Loss by Radiation. Similarly, the body loses heat by radiation when
the surrounding objects have surface temperatures lower than the temperature of the
body surface and gains heat by radiation when the temperature of surrounding surfaces
is above that of the body surface.
e. Heat Loss by Combinations of Air and Surrounding Objects.
Accordingly, temperature combinations of the air and the surrounding objects may exist
which result in heat gain by the body because of radiation, even if the air temperature is
below that of the body.
f. Body Responses. The enlargement of blood vessels in the skin and an
increase in the rate of the heartbeat are normal body responses to heat stress. While
these adjustments increase the temperature of the skin and thus increase heat loss by
conduction and radiation, they place a strain on the circulatory system. These factors
play important roles in the -cause of heat stress reactions.
g. Heat Loss Through Sweating. When the body cannot lose sufficient heat
by conduction and radiation, the activity of the sweat glands increases and heat loss by
evaporation of sweat becomes the important means of maintaining normal body
temperature. As the relative humidity of the air increases, however, evaporation of
sweat decreases, thus reducing the cooling function of the sweat. Excess sweating
may lead to a marked loss of water and salt from the body. The resulting dehydration
and loss of body salt add to the stress on the circulatory system.
OTHER FACTORS AFFECTING HEAT LOSS
Other major factors influencing the likelihood of heat injury include the physical work -
being performed and the physical condition of the individual.