Common heat stress terms
Acclimatization: the body’s ability to adapt to heat exposure up to a certain point.
Body core temperature: The temperature of the arterial blood irrigating the thermo-
regulatory centers in the hypothalamus.
Conduction: If the transfer of heat between materials that contact each other. Heat passes
from the warmer material to the cooler material. For example, a worker’s skin can transfer
heat to a contacting surface if that surface is cooler, and vice versa.
Convection: Is the transfer of heat in a moving uid. Air owing past the body can cool
the body if the air temperature is cool. On the other hand, air that exceeds 35oC (95oF) can
increase the heat load on the body.
Dry Bulb Temperature: The temperature of air as registered by a thermal sensor shielded
from direct radiant energy sources.
Evaporative Cooling: Takes place when sweat evaporates from the skin. High humidity
reduces the rate of evaporation and thus reduces the effectiveness of the body’s primary
cooling mechanism.
Globe Thermometer: A black copper sphere with an internal thermal sensor used to deter-
mine the effect of surrounding radiant heat.
Heat Index (HI): The Heat Index represents how an average person feels relative to climate
conditions. For a given temperature, the higher humidity, the higher the Heat Index.
Heat Stress: The total net heat load on the body which results from exposure to external
sources and from internal metabolic heat production.
Metabolic Heat: Heat produced by the body in relationship to work that the individual is
doing. The more strenuous the work, the higher the metabolic heat and the harder the body
has to work to eliminate it.
Micro- Environment: A self-contained environment, such as the inside of a hazardous
materials suit, in which thermal exchange with the surrounding air is limited.
