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Heat strain imposed by personal protective ensembles: quantitative analysis using a thermoregulation model

Abstract

The objective of this paper is to study the effects of personal protective equipment (PPE) and specific PPE layers, defined as thermal/evaporative resistances and the mass, on heat strain during physical activity. A stepwise thermal manikin testing and modeling approach was used to analyze a PPE ensemble with four layers: uniform, ballistic protection, chemical protective clothing, and mask and gloves. The PPE was tested on a thermal manikin, starting with the uniform, then adding an additional layer in each step. Wearing PPE increases the metabolic rates \( \left(\dot{\mathrm{M}}\right) \), thus \( \dot{\mathrm{M}} \) were adjusted according to the mass of each of four configurations. A human thermoregulatory model was used to predict endurance time for each configuration at fixed \( \dot{\mathrm{M}} \) and at its mass adjusted \( \dot{\mathrm{M}} \). Reductions in endurance time due to resistances, and due to mass, were separately determined using predicted results. Fractional contributions of PPE’s thermal/evaporative resistances by layer show that the ballistic protection and the chemical protective clothing layers contribute about 20 %, respectively. Wearing the ballistic protection over the uniform reduced endurance time from 146 to 75 min, with 31 min of the decrement due to the additional resistances of the ballistic protection, and 40 min due to increased \( \dot{\mathrm{M}} \) associated with the additional mass. Effects of mass on heat strain are of a similar magnitude relative to effects of increased resistances. Reducing resistances and mass can both significantly alleviate heat strain.

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Acknowledgments

The authors would like to thank Mr. Tim Rioux and Mr. Adam Potter for their constructive discussion and comments, and Ms. Linda Santee for proofreading. This article is approved for public release. The opinions or assertions contained herein are the private views of the author(s) and are not to be construed as official or reflecting the views of the Army or the Department of Defense. Any citations of commercial organizations and trade names in this report do not constitute an official Department of the Army endorsement of approval of the products or services of these organizations.

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Correspondence to Xiaojiang Xu.

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Xu, X., Gonzalez, J.A., Santee, W.R. et al. Heat strain imposed by personal protective ensembles: quantitative analysis using a thermoregulation model. Int J Biometeorol 60, 1065–1074 (2016). https://doi.org/10.1007/s00484-015-1100-0

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Keywords

  • Heat stress
  • Protective clothing
  • Thermal manikin
  • Modeling
  • Metabolic rate
  • Load carriage