Evaluation of a Novel Personal Cooling Device for Workers in Hot Environments

Abstract

Heat strain from the environment and clothing poses a serious threat in many occupational settings. Many personal cooling devices are limited in field use due to lack of mobility, limited cooling capacity, logistics, cost, and other factors. A non-powered cooling garment based on the endothermic expansion of liquefied carbon dioxide (CO2) has recently been developed. PURPOSE: To determine the effectiveness of this novel cooling device in reducing heat strain during work in a hot and humid environment. METHODS: Ten males completed two trials in an environment of 30°C WBGT (75% relative humidity) with a novel liquid carbon dioxide cooling shirt (CC) or with no cooling (NC) in a randomized order. Mean time-weighted workload of walking and arm curls for each individual equaled 465 W (400 Kcals/h). RESULTS: In the CC condition, work duration was significantly increased by 32% (97±36 min) compared to NC (74±26 min) (p<0.05). There was no significant difference between CC and NC for mean skin temperature across trials. The rectal temperature (Tre) was significantly lower for CC after 50 min (p<0.05). The mean heart rate, the delta Tre increase rate, and heat storage at 55 min (last point with n=8) were significantly lower in CC (p<0.05). Overall heat storage was 54±41 W (CC) and 72±40 W (NC) (p<0.05). Participants also indicated favorable subjective responses (comfort, etc.) for CC vs. NC (p<0.05). CONCLUSION: This novel cooling device attenuated heat strain and would increase productivity for personnel working in a hot and humid environment. Practical aspects of use, such as: cost, convenience, weight, cooling duration, and rise in ambient CO2 concentration in confined spaces, must also be considered. Support by a Grant from Kimberly-Clark and Porticool, Inc.