ABSTRACT
Fundamental knowledge has led to an understanding of heat stress and universal methods for considering heat stress and the thermal strain it leads to in people. To understand how people respond to heat and determine methods of assessment of human heat stress, it is important to recognize that people are objects in the universe and subject to its conditions. The heat balance equation for the human body is therefore a heat gain due to metabolic heat on one side of the equation, which equals (is balanced by) the sum of heat gains and heat losses by conduction, convection, radiation, evaporation, and condensation. Heat transfer by convection is due to the movement of fluid, and the heat is carried by the fluid itself. When people become hot, they feel it mainly through sensors in their skin, and they take any available opportunities to behave in a way which avoids or reduces the heat stress.
