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Evaluation of protective effect of fire suit
The thermal performance properties of firefighters'protective clothing are primarily based on the thermal comfort properties such as air permeability, thermal conductivity, thermal diffusivity, thermal absorptivity, water vapour permeability and water vapour resistance. This study aimed to analyze thermal comfort properties of two kinds of outer shell, moisture barrier and thermal barrier fabrics and multi-layered combinations of them used in firefighter clothings. Two types of firefighter uniforms were also evaluated using thermal camera and analyses were conducted to show the thermal distributions under the same environmental and physical conditions.
Important findings can be derived from the thermal comfort test results by comparing single layer fabrics with their multilayered combinations. Especially moisture barrier and thermal barrier fabrics have an important role on the multilayered fabric structure’s thermal conductivity and thermal resistance values. PU membrane with knitted fabric and Aramid felt quilted to Aramid/Viscose FR fabrics had lower thermal diffusivity and thermal resistance values and this leaded to lower thermal diffusion and thermal resistance characteristics in A1B1C1 structure (Nomex outer shell, PU membrane laminated to FR Knitted fabric moisture barrier and aramid felt quilted to aramid/viscose FR fabric thermal barrier). Thermal absorptivity gives the warm-cool feeling of fabrics and thermal absorptivity was found higher for A1B1C1 structure.
It was found that the overall moisture distribution in multilayered fabric combinations is mainly influenced by using specific combinations of outer shell, moisture barrier and thermal barrier fabrics. As it was concluded by Keiser et.al.[27] moisture content of clothing structure is depend on the fabric layer combinations because moisture is transferred to the more hydrophilic fabric layer. In this study it was found that first and second layers in firefighter clothings proved to have high importance in water permeability and water vapour resistance values of multilayered fabric combinations. Fabric types, A2 (PBI/ParaAramid) and B2 (PU membrane laminated to FR Nonwoven Fabric) had lower water vapour resistance values than A1(Nomex) and B1(PU membrane laminated to FR Knitted Fabric) and this leaded to a lower resistance value for the three layered fabric structure of A2B2C2. Moreover relative water permeability was higher for A2B2C2 because of A2 and B2 fabrics.
Statistical analysis were also conducted to find relationships for thermal conductivity, thermal absorptivity, thermal diffusivity, water vapour resistance and water vapour permeability results and it was found high correlation values.As a result of thermal comfort tests and thermal camera evaluations, it was found that type 2 firefighter clothing(A2B2C2) had less temperature increase than the type 1 clothing (A1B1C1) because of its better water permeability,moisture permeability, thermal diffusion and absorptivity properties. In the literature considering the case of firefighting, mostly Nomex and PBI fabrics were studied and compared. Nomex flame-resistant meta-aramid material was found to exhibit good flame resistance and good thermal comfort properties. Moreover, Polybenzimidazole(PBI) fibers offer improved flame resistance and retain its strength and flexibility after exposure to flame. In some studies, it was found that PBI fiber enhances good performance properties combining flame-resistance, thermal protection and comfort with its good moisture absorption property [28,29]. In this study, even though the fabric layer’s mass per unit area are very close to each other, their thicknesses and material properties are different from each other. Thus, differences in different fabric layers resulted different thermal comfort performances.
This study compared two firefighter uniforms (PBI and Nomex outer shell) that were mostly used types in fire situations. Since different structural properties of the fabric samples and firefighter clothings were used in the experiments, the results are only valid for these particular conditions. As a future study, it is aimed to study with Nomex and PBI fibers as the outer shell and combine them with different types of moisture barrier and thermal barrier fabrics. Then, the effects of different fabric combinations on the thermal comfort properties of firefighter uniforms will be considered and analyzed.