| Excessive exposure to heat stress can cause a host of heat-related illnesses. For laborers, job specific work demands and protective garments greatly increase the risk of succumbing to the effects of heat stress. Microclimate cooling has been used to control heat stress exposure where administrative or engineering controls are not adequate. This study tested the performance of four personal cooling vests for use with insulated protective clothing (gas extraction coveralls) in warm-humid (35°C, 50% relative humidity) and hot-dry (40°C, 30% relative humidity) conditions. On 10 separate occasions, 5 male volunteers walked on a treadmill to elicit a target metabolic rate of 300 watts, for 120 minutes, while wearing a (a) water cooled vest, (b) air cooled vest, (c) frozen polymer vest (FP) (d) liquid CO2 cooling (LCO2 ) vest, or (e) no cooling (NC). A three-way mixed effects ANOVA was used to assess the results and a Tukey's Honestly Significant Difference multiple comparison test was used to identify where significant differences occurred (rho < 0.05). The air, water, and FP systems produced significantly lower heat storage rates compared to NC. To the extent that the gas extraction coverall is worn in an environment between 30°C and 45°C and the rate of work is moderate, the FP, air and water vest were shown to manage heat storage well, reducing storage rate by about 48%, 56% and 65% respectively. |
