5
2. MEASUREMENTS
QUESTemp
°
32
The QUESTemp
°
32 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 QUESTemp
°
32 measures three parameters: ambient or dry
bulb temperature (DB), natural wet bulb temperature (WB), and globe
temperature (G).
In addition to the WBGT, the QUESTemp
°
32 measures relative humidity
(RH) and computes the Heat Index (HI) or Humidex. The QUESTemp
°
32,
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:
WBGT (indoor) = 0.7WB + 0.3G
WBGT (outdoor) = 0.7WB + 0.2G + 0.1DB
The resulting WBGT can then be compared to published charts showing the
allowable work-rest regimens (stay-times) for given work loads. Appendix A
of this manual shows the table published by the ACGIH.
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 70
°
F - 120
°
F (21
°
C -
49
°
C) 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 70
°
F - 109
°
F (21
°
C - 43
°
C) and a relative humidity range
