Common heat stress terms
Natural Wet Bulb Temperature:
used to measure the effect of humidity in air obtained by a
wetted sensor that is exposed to natural air movement.
Radiant Heat:
Heat which is transferred to cooler objects in the surrounding environment.
Workers can incur exposure to radiant heat from the sun, hot asphalt, machines and ovens.
Relative Humidity:
The ratio of the amount of water vapor in the air compared to the greatest
amount possible at a specific temperature.
WBGT (Wet Bulb Globe Temperature):
a weighted average which combines the effects of
humidity, air velocity, ambient air temperature and radiant energy into one single index. The
resulting WBGT values can be compared to indices of work-rest regimens (stay times) based
upon work loads.
WBGT (indoor) = 0.7WB + 0.3G (denoted as “WBGTi” on the display)
WBGT (outdoor) = 0.7WB + 0.2G + 0.1DB (denoted as “WBGTo” on the display)
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053-045 Rev.C 12/10
