Heat stress in chemical protective clothing: porosity and vapour resistance

Abstract

Heat strain in chemical protective clothing is an important factor in industrial and military practice. Various improvements to the clothing to alleviate strain while maintaining protection have been attempted. More recently, selectively permeable membranes have been introduced to improve protection, but questions are raised regarding their effect on heat strain. In this paper the use of selectively permeable membranes with low vapour resistance was compared to textile-based outer layers with similar ensemble vapour resistance. For textile-based outer layers, the effect of increasing air permeability was investigated. When comparing ensembles with a textile vs. a membrane outer layer that have similar heat and vapour resistances measured for the sum of fabric samples, a higher heat strain is observed in the membrane ensemble, as in actual wear, and the air permeability of the textile version improves ventilation and allows better cooling by sweat evaporation. For garments with identical thickness and static dry heat resistance, but differing levels of air permeability, a strong correlation of microclimate ventilation due to wind and movement with air permeability was observed. This was reflected in lower values of core and skin temperatures and heart rate for garments with higher air permeability. For heart rate and core temperature the two lowest and the two highest air permeabilities formed two distinct groups, but they did not differ within these groups. Based on protection requirements, it is concluded that air permeability increases can reduce heat strain levels allowing optimisation of chemical protective clothing. STATEMENT OF RELEVANCE: In this study on chemical, biological, radiological and nuclear (CBRN) protective clothing, heat strain is shown to be significantly higher with selectively permeable membranes compared to air permeable ensembles. Optimisation of CBRN personal protective equipment needs to balance sufficient protection with reduced heat strain. Using selectively permeable membranes may optimise protection but requires thorough consideration of the wearer's heat strain.

Physiological Evaluation of Cooling Devices in Conjunction With Personal Protective Ensembles Recommended for Use in West Africa

“…isk for heat-stress-related injuries is increased greatly for occupations that require wearing of impermeable or nonporous personal protective equipment (PPE) while working in hot and humid environments. 1,2 One of several possible examples of such an occupation is health care workers (HCWs) who have been called to respond to the Ebola outbreak in West Africa. While heightened transmission-based precautions for HCWs treating Ebola patients provide elevated protection from pathogens, these precautions require additional layers of PPE that can increase the burden of heat stress.…”

Chemical, biological, radiological and nuclear (CBRN) protective clothing

“…This lighter-weight ensemble was made possible by technological advances in the manufacture of adsorptive carbon fabrics that were thinner than the previously used carbon polyurethane foams (Endrusick et al ., 2005 ). Since the introduction of the JSLIST ensemble, most of the research into CBRN materials has focused on replacing the carbon fabrics with semipermeable membranes that allow the transmission of moisture vapor but block the transmission of chemical agents (Endrusick et al ., 2005 ;Havenith et al ., 2011 ). One of the goals for semipermeable membranes is to incorporate the protection directly into the standard uniform and eliminate the need for a protective overgarment, thus reducing the thermal burden without affecting the level of protection.…”

Effect of Protective Clothing and Fatigue on Functional Balance of Firefighters

“…Wearing PPE may impair the functional balance of firefighters due to its heavy weight, bulkiness of the material, and a SCBA face mask, which limits vision [4,5]. Wearing PPE also changes the firefighter's center of gravity [6], increases fatigue [7], and imposes physiological burdens, e.g., increased oxygen consumption and heart rate [7][8][9][10]. The heavy, insulative aspect of PPE also contributes to increased metabolic work done by the firefighter, resulting in increased heat stress [11,12] that might negatively impact functional balance.…”