2 Measurements
QUESTemp32
The QUESTemp32 portable area heat stress monitor computes the Wet Bulb Globe
Temperature (WBGT). The WBGT is an accepted measurement for determining the heat
stress level imposed on an individual in a given environment. The QUESTemp32
measures three parameters: ambient or dry bulb temperature (DB), natural wet bulb
temperature (WB), and globe temperature (G).
In addition to the WBGT, the QUESTemp32 measures relative humidity (RH) and
computes the Heat Index (HI) or Humidex. The QUESTemp32, using inputs on the side
of the instrument, has the ability to connect to two additional sensor arrays for monitoring
up to three locations simultaneously.
Wet Bulb Globe Temperature
The WBGT is a weighted average of the three temperature sensors using the following
formulas:
NOTE: The resulting WBGT can be compared to indices of work-rest regimens (stay
times) based upon the work loads. (Please see Appendix A for published heat
exposure tables.)
Heat Index / Humidex
The Heat Index is determined using the dry bulb temperature and relative humidity.
Based upon charts available from the U.S. National Weather Service, Heat Index
represents how an average person feels relative to climate conditions. For a constant
temperature, if the humidity rises, so does the heat index.
The Heat Index is defined over a temperature range of 70F - 120F (21C - 49C) and a
relative humidity range of 30% - 99%. Outside of this range, the instrument will show
dashes in the display for the Heat Index.
The Humidex is used primarily in Canada and is very similar to the Heat Index. The
values are slightly different. The Humidex is defined over a temperature range of 70F -
109F (21C - 43C) and a relative humidity range of 20% - 99%. Outside of this range,
the instrument will show dashes in the display for the Humidex.
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)