Casella CEL Microtherm WBGT heat stress monitor - Manual (Page 7)

1. DESCRIPTION OF THE MICROTHERM
1.1 Background
A person's thermal comfort is mainly related to the thermal balance of their
body as a whole. This balance is influenced by their physical activity and
clothing, as well as the environmental parameters of, air temperature, mean
radiant temperature, air velocity and air humidity.
Problems of heat stress are common in workplaces such as foundries, steel
mills, brick glass and ceramic factories, power generation plants, coke ovens,
laundries, modern glass buildings with inadequate air conditioning, mines and
many other types of outdoor work in hot climates.
Whenever heat stress is imposed on the human body, there is a resulting
strain which may result in physiological reactions such as sweat production,
increased heart rate and higher core temperature. The greater the heat
stress, the greater heat strain and under certain conditions, the latter may
attain such magnitude as to cause damage to health.
Several indices have been designed to integrate the environmental factors
contributing to heat stress and one such index is the Wet Bulb Globe
Temperature Index. The WBGT index was initially developed to provide a
simple method for assessment of heat stress among military personnel. The
Microtherm Heat Stress WBGT determines two WBGT values.
For inside applications and outside measurements with no solar load, the
WBGT inside value is used.
WBGTin = 0.7tnw + 0.3ta
For outside measurements with solar load, the WBGT outside value is used.
WBGTout = 0.7tnw + 0.2tg + 0.1ta
Higher exposures to heat than those shown in Table 1 are permissible if the
workers have been undergoing medical surveillance and it has been
established that they are more tolerant to work in heat than the average
worker. Workers should not be permitted to continue their work when their
deep body temperature exceeds 38 o C.
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Description MICROTHERM Heat Stress WBGT &
WinHSM Application Software - User Manual