Thermal protective performance of protective clothing used for low radiant heat protection

Abstract

A laboratory simulation was performed to study the thermal protective performance of fabric systems under low level thermal hazards in the range of 6.3—8.3 kW/m2 . Two approaches were used. The first used a method similar to the ASTM F 1939, radiant heat resistance test, while the second used a modification designed to capture the contribution to skin burn injury due to energy stored in the test specimens being released after the direct exposure had ended. Both dry and wet specimens were tested. In order to accommodate the prolonged exposure time a water cooled heat flux sensor was used to calibrate the radiant heat source and measure the energy directly transmitted through during the exposure and discharged later from the fabric systems. The Henriques Burn Integral (HBI) was adopted and programmed with a three layer skin model to predict the time required to achieve a second degree skin burn injury. The study investigated the thermal protection provided by the clothing with different layering and examined the effect of moisture under low level radiant heat exposures. In addition, the physiological burden associated with wearing the clothing was predicted and compared. The results obtained show the difference in measured protection level under low radiant heat from these two approaches and demonstrate that the stored thermal energy released from the clothing system significantly lowers the measured thermal protective performance.

Quantitatively assessing the effect of exposure time and cooling time of fabric assemblies representative of those used in firefighter clothing on the thermal protection

“…Interestingly, this behavior is observed also when the stored energy effect is considered. Previous studies have shown that the heavier fabric systems and those with air layers, while providing better thermal insulation , also possess superior capacity to store greater amounts of thermal energy, which can be subsequently released to the skin during cooling after exposure to heat . However, it must be noted that this improved thermal insulation works not only during exposure but also during the cooling of the fabric assembly.…”

“…This is especially useful for the determination of TPE values: the iterative method requires the experimenter to expose the specimen several times to heat, with each trial's exposure time adjusted according to the previous trial's result. This is very time‐consuming, and sometimes only an approximate result can be obtained . The proposed regression method provides a suitable means to determine the TPE values more conveniently.…”

“…These factors should continue to be evaluated when the stored thermal energy effect is considered. Regarding the effects of clothing and heat source intensity, several researchers have examined the influences of air gaps between fabric and human skin on the thermal protective performance of clothing , as well as the effects of moisture contained within fabrics and the level of heat flux . The results showed that the protective performance of clothing can be significantly affected by the stored energy .…”

Effects of clothing and fibres properties on the heat and mass transport, for different body heat/sweat releases

“…This knowledge is also very relevant when developing automotive environments or artificial microclimates for workplaces [4,5]. Several thermal manikins and experimental procedures have been developed to evaluate the performance of different types of products under various conditions [6][7][8][9][10][11]. Zhao et al [6] used a thermal manikin to study the influence of design features of a ventilated clothing on cooling performance, while Elabbassi et al [10] used a similar approach to analyse the efficiency of an electric-heated blanket in preventing hypothermia in neonates.…”

“…Zhao et al [6] used a thermal manikin to study the influence of design features of a ventilated clothing on cooling performance, while Elabbassi et al [10] used a similar approach to analyse the efficiency of an electric-heated blanket in preventing hypothermia in neonates. The usual procedure consists of setting constant temperature or heat flux on the manikin surface [6,[8][9][10], corresponding to skin values of an human in a state of thermal comfort. Recently, the surface temperature and sweat rates of some thermal manikins have been controlled by mathematical models of human thermoregulation [7,12,13].…”