SEDL / STP / STP1133-EB / STP19188S

Heat Strain Produced by 3 Aircrew Chemical Defence Ensembles Under Hot Conditions: Improvement with an Air-Cooling Vest

Vallerand, AL
Defence and Civil Institute of Environmental Medicine, North York, Ontario

Schmegner, IF
Defence and Civil Institute of Environmental Medicine, North York, Ontario

Michas, RD
Defence and Civil Institute of Environmental Medicine, North York, Ontario

Pages: 14    Published: Jan 1992

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Abstract

The heat strain produced by three different Canadian Forces chemical defence (CD) individual protection ensembles (IPE) was studied under simulated hot cockpit conditions with an air-cooling vest (AC) and with no cooling (NC). Seven healthy males were randomly subjected to six heat stress tests (37°C, 50% r.h., target of 150 min) using the helicopter IPE with AC-4 mask (H4), the helicopter IPE with AR-5 hood/respirator (H5), and the CF-18 fighter IPE (F) with AR-5 respirator and anti-G suit. Whatever the IPE, AC increased heat exposure time and total heat losses, and decreased the change in core (δT^re/h) and whole body mean skin temperatures (δ¯T^sk(WB)/h) (P<0.05). Differences within IPEs appeared restricted to the F-NC condition. F-NC produced a lower heat exposure time (vs H4-NC and H5-NC) and sweat evaporation rate (vs H4-NC), and a greater δ¯T^sk(WB)/h (vs H4-NC and H5-NC) and T^re at min 80 (vs H5-NC) (P<0.05). The results demonstrate that air cooling greatly enhances heat tolerance of subjects wearing any of the 3 CD IPEs tested. They also indicate that without cooling, both helicopter IPEs produce slightly better tolerance to heat than the fighter IPE, possibly an influence of the anti-G suit on evaporative cooling.