Dynamics of the Formation of Microclimatic Conditions Causing Uncompensated Heat Stress in Firefighting Protective Clothing

Abstract

This research examined the dynamics of microclimate changes within firefighter protective clothing and their effect on core body temperature. The basic question of the study was whether microclimatic factors causing heat stress can develop in firefighter protective clothing during the initial phase of interventions, before the actual firefighting. How do core temperature and skin temperature change, and at what rate does uncompensated heat stress build up? Is there a significant difference between the physiological indicators of exertion performed while wearing protective clothing and those performed in sportswear, under the same working conditions and external environmental conditions? In a 35-minute exercise test performed in the protective clothing (BEV) and sportswear (control, KON) at a specified load of 9±1 MET units, the results between the groups showed a significant difference between the core body temperature (Tc) values of the two groups. In the BEV group (mean [M]=38.36; standard deviation [SD]=0.116) and the KON group (M= 37.99; SD=0.055), the Tc values showed a significant (p=0.010) difference. In the case of the heart rates (HR) detected at the end of the test, statistical analysis also showed a significant difference between the BEV (M= 163.4; SD=8.414) and KON (M= 133; SD=9.848) groups (p=0.0127). The data show that, under the same external load, neither the core temperature, skin temperature, nor heart rate in the control group reached the values of the BEV group. The microclimate inside the protective clothing was characterized by an average air temperature of 33.58°C (SD 1.03) and the relative humidity was 80.95% (SD 9.89). The results confirm the assumption that in the initial phase of the interventions, microclimatic conditions may develop inside the protective clothing that can lead to uncompensated heat stress. Further mathematical and statistical analysis of the measurement data showed that markers indicating uncompensated heat stress typically appeared between the 15th and 18th minutes in members of the BEV group.