Effects of Hoods and Flame-Retardant Fabrics on WBGT Clothing Adjustment Factors

Abstract

Personal protective clothing (PPC) may include hoods and flame-retardant (FR) fabrics that may affect heat transfer and, thus, the critical wet bulb globe temperature (WBGT_crit) to maintain thermal equilibrium. The purpose of this study was to compare the differences in WBGT _crit for hooded vs. nonhooded versions of particle barrier and vapor barrier coveralls as well as for coveralls made of two flame-retardant fabrics (INDURA cotton and Nomex). Acclimated men (n = 11) and women (n = 4) walked on a treadmill in a climatic chamber at 180 W/m ² wearing four different ensembles: limited-use, particle barrier coveralls with and without a hood (Tyvek 1427), and limited-use vapor barrier coveralls with and without a hood (Tychem QC, polyethylene-coated Tyvek). Twelve of the participants wore one of two flame-retardant coveralls. All participants wore standard cotton clothing. Progressive exposure testing at 50% relative humidity (rh) was designed so that each subject established a physiological steady-state followed by a clear loss of thermal equilibrium. WBGT _crit was the WBGT 5 min prior to a loss of thermal equilibrium. Hooded ensembles had a lower WBGT _crit than the nonhooded ensembles. The difference suggested a clothing adjustment of 1°C for hoods. There were no significant differences among the FR ensembles and cotton work cloths, and the proposed clothing adjustment for FR coveralls clothing is 0°C.

Keywords:

• heat stress
• protective clothing
• WBGT

ACKNOWLEDGMENTS

The authors would like to thank the participants and laboratory support, including Christina Luecke. This research was supported by a grant from the National Institute for Occupational Safety and Health.

Article contents are solely the responsibility of the authors and do not necessarily represent the official views of NIOSH, CDC, United States Air Force, or the Department of Defense.

Notes

^A Discrepancy in differences between the means is due to one missing data point for each hood condition (n = 28 rather than 30 total). The value reported in the table is the difference in the least squares means from the general linear model analysis instead of the 1.4 between the two combined means.