Effects of uniforms on firefighters thermal stresses

Abstract

The purpose of this investigation was to develop and verify a heat stress index called "equivalent effective temperature of clothing microclimate"(TEEcmc). TEEcmc was used to identify the thermal stress in firefighter rescue activities when they wore high heat insulated personal protective equipment (PPE). Moreover, a computer simulation, S-smart, was used to verify TEEcmc in different wearing conditions and compare the effects of firefighter uniform's fabric and assemblies on the physiological responses. The measured physiological responses included core temperature (Tcore), Heart Rate (HR), Skin Temperature (Tskin), and microclimate Temperature and relative humidity (Tcmc & RHcmc) between skin and uniform. The wear trial experiments were held in the training facilities in Hong Kong Fire Service Department West Kowloon Rescue Training Centre and climate chamber in Hong Kong Polytechnic University. After experiments, S-smart was also used to simulate the effects of fabric properties and design of uniform on the thermal stress of the firefighters. The results of the clothing microclimate temperature and humidity indicated that the firefighters had been exposed to the danger category of heat illness during simulated-firefighting training. From the experimental data, a new microclimate index, TEEcmc was developed for the prediction of thermal stress of firefighters. This proposed index was verified in another wear trial conducted in a climate chamber and computer simulation using S-smart. In both wear trials during walking and resting, there was a positive linear relationship between physiological strain index (PSI) and TEEcmc. In the S-smart simulation, it also showed a positive linear relationship between the simulated Tcore and TEEcmc during walking but not resting. This implies that TEEcmc is a useful index of thermal stress and more convenient to use because the microclimate temperature and humidity can be directly measured. Based on three pairs of comparison of clothing fabrics and designs revealed that moisture managed fabric, single layer clothing and short-sleeve uniforms caused a lower thermal stress in the climate chamber wear trial. These results matched with that in S-smart simulation. The Originality of this study is the newly-developed heat stress index TEEcmc in high-risk occupations such as firefighters, this index has been successfully verified by a wear trial and computer simulation of thermal stress in different clothing designs and fabric properties.