Protection of workers in hot environments requires
a means of identifying conditions where excessive
thermal stress places their health at risk. International
Standard ISO 7933:2004 (ISO, 2004) uses the predicted
heat strain index, but the complexity of this index
discourages its use. In commoner use is the Wet
Bulb Globe Temperature (WBGT), and the ACGIH
TLV is in terms of this (ACGIH, 2007). The shortcomings
of WBGT are widely recognized (Brake
and Bates, 2002b; Taylor, 2006) and include the need
to estimate metabolic rates and its relative insensitiv-
ity to the cooling effect of air movement. In practice,
the WBGT is often seen to be excessively conservative
and is largely ignored in many situations where
its rigorous implementation would lead to unacceptable
and unnecessary losses in productivity.
Advances in instrumentation have led to the publi-