WBGT clothing adjustment factors for four clothing ensembles and the effects of metabolic demands.
Bernard TE; Caravello V; Schwartz SW; Ashley CD
J Occup Environ Hyg 2008 Jan; 5(1):1-5
This study measured the clothing adjustment factors (CAFs) for four clothing ensembles (Cotton Coveralls, Tyvek 1427 Coveralls, NexGen Coveralls, and Tychem QC Coveralls; all coveralls were worn without hoods) against a baseline of cotton work clothes to determine whether the CAFs would be affected by the metabolic rate. Fifteen participants wore one of the five ensembles while walking on a treadmill at low, moderate, and high rates of work in an environment maintained at 50% relative humidity. A climatic chamber was used to slowly increase the level of heat stress by increasing air temperature. When the participant's core temperature reached a steady-state, the dry bulb temperature was increased. The point at which the core temperature began to increase was defined as the inflection point, and the WBGT recorded 5 min before the inflection point was the critical WBGT for each ensemble. A three-way mixed effects linear model with ensemble by metabolic rate category interactions demonstrated that the CAF did not change with metabolic rate, so CAFs can be used over a wide range of metabolic rates. The data at the moderate metabolic rate were combined with data on 14 participants from a previous study under the same conditions. The CAFs in degrees C WBGT were 0 for cotton coveralls, 1.0 for Tyvek 1422A, and 2.5 for NexGen. Although the value of 7.5 for Tychem QC was found, the recommendation remained at 10 to account for the effects of humidity. The standard error for the determination of WBGT crit at 50% relative humidity was 1.60 degrees C WBGT.
Humidity; Clothing; Heat; Heat exposure; Heat stress; Physiological testing; Environmental factors; Air temperature; Temperature effects; Temperature control; Protective clothing; Statistical analysis; Threshold limit values; TLV; Body temperature; Metabolic rate;
Author Keywords: heat stress; metabolic rate; protective clothing; TLV
Thomas E. Bernard, University of South Florida, College of Public Health, 13201 Bruce B. Downs Blvd., Tampa, FL 33612-3805
Research Tools and Approaches: Exposure Assessment Methods
Journal of Occupational and Environmental Hygiene
University of South Florida, Tampa, Florida