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Evaluation of protective ensemble thermal characteristics through sweating hot plate, sweating thermal manikin, and human tests.

Authors
Kim-J-H; Powell-JB; Roberge-RJ; Shepherd-A; Coca-A
Source
J Occup Environ Hyg 2014 Apr; 11(4):259-267
NIOSHTIC No.
20043832
Abstract
The purpose of this study was to evaluate the predictive capability of fabric Total Heat Loss (THL) values on thermal stress that Personal Protective Equipment (PPE) ensemble wearers may encounter while performing work. A series of three tests, consisting of the Sweating Hot Plate (SHP) test on two sample fabrics and the Sweating Thermal Manikin (STM) and human performance tests on two single-layer encapsulating ensembles (fabric/ensemble A = low THL and B = high THL), was conducted to compare THL values between SHP and STM methods along with human thermophysiological responses to wearing the ensembles. In human testing, ten male subjects performed a treadmill exercise at 4.8 km and 3% incline for 60 min in two environmental conditions (mild=22.C, 50% relative humidity (RH) and hot/humid = 35.C, 65% RH). The thermal and evaporative resistances were significantly higher on a fabric level as measured in the SHP test than on the ensemble level as measured in the STM test. Consequently the THL values were also significantly different for both fabric types (SHP vs. STM:191.3 vs. 81.5 W/m2 in fabric/ensemble A, and 909.3 vs.149.9 W/m2 in fabric/ensemble B (p < 0.001). Body temperature and heart rate response between ensembles A and B were consistently different in both environmental conditions (p < 0.001), which is attributed to significantly higher sweat evaporation in ensemble B than in A (p < 0.05), despite a greater sweat production in ensemble A (p < 0.001) in both environmental conditions. Further, elevation of microclimate temperature (p < 0.001) and humidity (p < 0.01) was significantly greater in ensemble A than in B. It was concluded that: (1) SHP test determined THL values are significantly different from the actual THL potential of the PPE ensemble tested on STM, (2) physiological benefits from wearing a more breathable PPE ensemble may not be feasible with incremental THL values (SHP test) less than approximately 150-200 Wm2, and (3) the effects of thermal environments on a level of heat stress in PPE ensemble wearers are greater than ensemble thermal characteristics.
Keywords
Personal-protective-equipment; Heat-loss; Thermal-reactions; Body-temperature; Fabrics; Laboratory-testing; Simulation-methods; Temperature-effects; Heat-exchange; Humans; Physiological-response; Physiological-testing; Relative-humidity; Humidity; Heart-rate; Protective-clothing; Protective-materials; Heat-stress; Work-clothing; Author Keywords: total heat loss; thermal resistance; vapor permeability; core temperature; evaporative heat loss
Contact
Dr. Aitor Coca, National Personal Protective Technology Laboratory (NPPTL/NIOSH/CDC), 626 Cochrans Mill Road, B29-107, Pittsburgh, PA 15236
CODEN
JOEHA2
Publication Date
20140401
Document Type
Journal Article
Email Address
esq6@cdc.gov
Fiscal Year
2014
NTIS Accession No.
NTIS Price
Identifying No.
M022014
Issue of Publication
4
ISSN
1545-9624
NIOSH Division
NPPTL
Source Name
Journal of Occupational and Environmental Hygiene
State
PA
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