2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
pairs of gloves. A third trial was for participants in shorts and T-shirt. In each trial
participant wore a face-mask and breathing apparatus connected to a compressed air
source.
RESULTS
Study 1: The numerical model was tested against a sweating hot plate and a manikin
with a wetted surface, showing good agreement (within 15%) as ambient temperature
was varied from 10 to 35 °C. Heat and mass transport coefficients were initially
estimated then refined on the basis of the manikin results. The predictions for skin
heat loss in an environment of 33°C and 30% RH for a subject with 1.7m 2 skin
surface area were 25W without wetting and 140W with wetting of the suit surface.
This assumed a slow walk of the participant does not change the heat loss
significantly compared to the static manikin. For a standard subject mass of 70 kg and
an average specific heat of the body of 3.8 kJ/ kg °C, this gives a potential reduction
in the rate of increase of MBT by 1.7°C/h.
Study 2: The mean duration of the exercise completed was 72 ± 9 min in the dry-suit,
116 ± 5 min in wetted-suit and 119.4 ± 0.5 min in the shorts and T-shirt conditions.
The average rates of increase in MBT were 1.38°C/h in the dry-suit, 0.18°C/min in
the wetted-suit and 0.19°C/h in shorts and T-shirt conditions. This gave an estimated
rate of heat storage of 103.7 W in the dry suit, 13.4 W in the wetted suit and 14.8 W
in the shorts and T-Shirt conditions. The estimated reduction in the rate of increase of
mean body temperature due to wetting of the suit surface was 1.2°C/h.
DISCUSSION
The numerical estimate for the reduction in the rate of increase of mean body
temperature between a dry- and wetted-impermeable chemical-biological protective
suit was 1.7°C/hr. The human data supported that the reduction in the rate of increase
of mean body temperature was 1.2°C/hr. It is concluded that while the reduction in
the rate of rise is less than that estimated by the numerical model, surface wetting of
an impermeable chemical-biological protective suit is an effective means to reduce
heat strain in exercising humans.
ACKNOWLEDGEMENTS
This research was supported by: W.L. Gore & Associates, Inc, Canadian Institutes of
Health Research, Natural Sciences and Engineering Council of Canada and the
Canadian Foundation for Innovation.
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