Total heat loss as a predictor of physiological response in wildland firefighter gear

Abstract

In most types of protective clothing heat strain is an important issue. The wildland firefighter clothing system in the USA has seen no major revision over the last decades. In this project the wildland firefighter clothing system was studied at the material and the systems level. On the sweating guarded hot plate and the sweating thermal manikin effects of different base layers (cotton and modacrylic) and meta-aramid outer layers of different fabric weights were evaluated. Then, a human subject trial was performed on a limited set of clothing systems to validate the results from materials and manikin testing. The clothing systems were composed of relevant materials for wildland firefighters with extra configurations added to explore the effects of the highest and lowest levels of protection. All measurement techniques were reverted to a calculation of the total heat loss (THL), as predicted from the hot plate and the manikin and compared to the calculated heat loss from the human subjects. The prediction of the heat strain, based on the sweating guarded hot plate only, gives a large overestimation of the actual heat loss in humans. The currently used standard in the USA that utilizes THL values has no link to actual human heat loss. The manikin showed much better comparison to the human data in absolute terms, but in general underestimated heat loss and showed worse overall correlation to the human heat loss data than the hot plate values.

Fractional Contribution of Wildland Firefighters’ Personal Protective Equipment on Physiological Strain

“…The increase in T gi found in this study ( Figure 2 ) seems to indicate that the subjects reached a situation of uncompensable heat stress during the tests ( Den Hartog et al, 2016 ). It has been previously reported that a temperature above 38°C may be a limiting factor of performance during exercise in the heat ( González-Alonso et al, 1999 ).…”

“…In general, the PPC protective characteristics may interfere with thermoregulation, reducing or preventing the heat transfer and sweat evaporation ( Holmér, 2006 ; Cheung et al, 2010 ; Carballo-Leyenda et al, 2017 ). Therefore, the study of the wildland firefighters’ thermophysiological response to different PPC has acquired special relevance in recent years ( Den Hartog et al, 2016 ; Carballo-Leyenda et al, 2017 ).…”

“…To our knowledge, there is a paucity of studies on the wildland firefighters’ PPE physiological impact ( Budd et al, 1997 ; Den Hartog et al, 2016 ). Initial work of Budd et al (1997) compared the thermophysiological response of two PPE with different thermal insulation levels.…”

“…Initial work of Budd et al (1997) compared the thermophysiological response of two PPE with different thermal insulation levels. More recently, Den Hartog et al (2016) analyzed the influence of several PPE on thermal balance according to different fabric composition and structure (i.e., wave and layers). The thermophysiological and subjective response of different PPC has also been recently studied ( Carballo-Leyenda et al, 2017 ).…”

“…This was probably due to the protocol performed. This study ( Carballo-Leyenda et al, 2017 ) employed a protocol with a moderate metabolic rate, similar to those previously mentioned ( Budd et al, 1997 ; Den Hartog et al, 2016 ). However, the need to increase the exercise intensity to accentuate the differences between PPC has been reported ( Kofler et al, 2015 ; Fontana et al, 2017 ).…”