Firefighter Equipment Operational Environment: Evaluation of Thermal Conditions
Authors:   UL Firefighter Safety Research Institute, Madrzykowski Daniel 
Published: December 2021

The goal of this study was to review the available literature to develop a quantitative description of the thermal conditions firefighters and their equipment are exposed to in a structural fire environment. The thermal exposure from the modern fire environment was characterized through the review of fire research studies and fire-ground incidents that provided insight and data to develop a range of quantification. This information was compared with existing standards for firefighting protective equipment to generate a sense of the gap between known information and the need for improved understanding. The comparison of fire conditions with the thermal performance requirements of firefighter protective gear and equipment demonstrates that a fire in a compartment can generate conditions that can fail the equipment that a firefighter wears or uses. The review pointed out the following: 1. The accepted pairing of gas temperature ranges with a corresponding range of heat fluxes does not reflect all compartment fire conditions. There are cases in which the heat flux exceeds the hazard level of the surrounding gas temperature. 2. Thermal conditions can change within seconds. Experimental conditions and incidents were identified in which firefighters would be operating in thermal conditions that were safe for operation based on the temperature and heat flux, but then due to a change in the environment the firefighters would be exposed to conditions that could exceed the protective capabilities of their PPE. 3. Gas velocity is not explicitly considered within the thermal performance requirements. Clothing and equipment tested with a hot air circulating (convection) oven are exposed to gas velocities that measure approximately 1.5 m/s (3 mph). In contrast, the convected hot gas flows within a structure fire could range from 2.3 m/s (5 mph) to 7.0 m/s (15 mph). In cases where the firefighter or equipment would be located in the exhaust portion of a flow path, while operating above the level of the fire, the hot gas velocity could be even higher. This increased hot gas velocity would serve to increase the convective heat transfer rate to the equipment and the firefighter, thereby reducing the safe operating time within the structure. 4. Based on the limited data available, it appears currently available protective clothing enables firefighters to routinely operate in conditions above and beyond the "routine" conditions measured in the fire-ground exposure studies conducted during the 1970s. The fire service and fire standards communities could benefit from an improved understanding of: • real world fire-ground conditions, including temperatures, heat flux, pressure, and chemical exposures; • the impact of convection on the thermal resistance capabilities of firefighting PPE and equipment; and • the benefits of balancing the thermal exposures (thermal performance requirements) across different components of firefighter protective clothing and safety equipment. Because it is unlikely due to trade offs in weight, breathe-ability, usability, cost, etc., that fireproof PPE and equipment will ever be a reality, fire officers and fire chiefs need to consider the capabilities of the protection that their firefighters have when determining fire attack strategies and tactics to ensure that the PPE and equipment is kept within its design operating environment, and that the safety buffer it provides is maintained.