Micro-environment changes inside impermeable protective clothing during a continuous work exposure

Protective clothing (PC) results in a micro-environment between itself and the body. Workers are then exposed to a heat stress greater than the ambien t environment alone, which is a reflection of micro-environment, metabolic rate and time. Adjustments to the ambient environment to account for the mi croenvironment have been formulated as a means to predict heat strain for s afety and productivity purposes. Measurement of the actual micro-environmen t was made for a mean of 63.1+/-7.9 min using a remote sensor at the should er, hip and thigh levels on 15 subjects during a continuous work protocol ( 300 kcal/h) in impermeable PC at an ambient temperature of 30.1 degreesC we t bulb globe temperature (WBGT) (32 degreesC dry, 29 degreesC wet, 33 degre esC globe). Micro-environment temperature increased over the duration of th e work period. There was no statistically significant difference (p>0.05) b etween the measurements made at the three different body sites for temperat ure or humidity. The mean micro-environmental WBGT at the end of work was 3 4.6 degreesC WBGT. Micro-environment WBGT increased rapidly in the first 20 min of work then slowed, rising only 0.5 degreesC WBGT from 40 to 60 min. These results suggest that at this particular high ambient temperature (30. 1 degreesC WBGT) an adjustment factor of 5 degreesC WBGT would give a more accurate indication of thermal stress for up to 1 h of continuous moderate work within PC. For shorter work durations, an even smaller adjustment woul d be appropriate.