The rate among the 85 and older patient is nearly five times that of all other age groups combined. Heat related deaths are very closely related to environmental temperature. Additionally, the risk of heat related injury is much higher in people whose normal compensatory mechanisms are impaired by advanced age, drugs, and chronic illness. A heat balance can be constructed to evaluate the different mechanisms for body heat gain and loss. There are four generally accepted mechanisms of heat transfer- radiation, conduction, convection, and evaporation.
Radiation is the transfer of heat between two objects in the form of electromagnetic energy.
Radiation transfer occurs any time there is a temperature difference between two objects that are in view of each other. It is the process by which the sun transmits energy to the earth. It can be easily experienced by simply feeling the warmth of the sun while sunbathing. Conduction is heat transfer between two objects that are touching each other, for example, placing one's hand on a hot stove. Convection is heat transfer from flow of a fluid or gas over an object.