Protective helmets used by fire-fighters must be designed to minimize the amount of heat transferred to the users head while providing durability, comfort, and affordable costs. This thesis highlights the evaluation of new helmet technology specifically tailored to high radiant heat environments to advance the state-of-the-art in head protection for this application. The research focused on the assessment of the outer shells of helmets and the properties of the surfaces. The development included the evaluation of radiation heat transfer, in a laboratory environment, to various helmet shell surface constructions. Industry standards were considered, and critiqued. Experiments were designed to isolate critical design variables for measurement and evaluation. Custom, purpose-built laboratory apparatus for testing helmets were designed, explained and utilized in the testing of specimens. Additionally, market demands for firefighting helmets were explored. Helmet durability was specifically addressed with abrasion criteria established and the reflectivity effects of the abraded surfaces evaluated. Resulting from this study, new surface technologies were identified for possible development in future helmet designs. Various surface materials, finishes, and coatings were compared and contrasted to current industry state-of-the-art equipment. The knowledge discovered further advanced modern head protection science in aim of increased safety and performance of fire-fighting personnel.

Modern firefighter protective equipment is excellent at protecting firefighters from surrounding heat, but how effective is at deflecting incoming radiant heat, and would the use of more reflective textiles, be able to further increase the equipment’s protective properties? This study aims to understand the different properties that reflective materials, compared to standard firefighter outer layers, have against radiative heat flux. The textiles of firefighter turnout gear and the reflective textiles used in the smelting industry have been examined when exposed to varying levels of radiant heat in a cone calorimeter. The materials were examined before and after a layer of soot was applied to them, to understand their capabilities if used in a soot-rich environment. The change in material emissivity, when soot was applied, could then be calculated for each material. The heat reducing properties of the sooted and non sooted materials emissivities were tested, using computer simulations of a firefighter’s full turnout gear. First the radiative and convective heat fluxes were compared within a computational fluid dynamics software called FDS, second the skin level temperature was calculated using VGP, a finite element software that accounts for heat flow further into the skin and body.  During the experiment it was found that the emissivity of the reflective material even after soot application, performed better than that of the standard firefighter gear. In the simulations, the sooted reflective material emissivity would reduce the total heat flux to the firefighter with an average of 19% compared to the sooted standard turnout gear. Using the temperature of 44 °C as the limit for human skin damage, the use of a reflective emissivity would allow a 19% longer exposure to the same incident heat before possible skin damage would occur. Reducing the emissivity of current turnout gear would prove valuable as a method of reducing heat accumulation in a firefighter, especially at key areas more susceptible to the radiative heat flux from smoke-layers and radiative flames. This would in turn provide safer work environments for structural firefighting by reducing heat stress during active operations.

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