Fire Protection Engineering Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2772
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Item Experimental Characterization of the Thermal Response of Firefighter Protective Ensembles Under Non-Flaming Convective Exposure(2024) DiPietro, Thomas Phillip; Raffan-Montoya, Fernando; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Thermal burns are one of the most serious injuries a firefighter can sustain while operating in a structure fire despite being fully covered in gear designed to protect them from thermal exposure. Extensive experimentation has been conducted into the performance of a firefighter’s protective ensemble when caught in a high radiative heat flux environment to ensure the wearer has enough time to escape to safety. High heat flux tests are beneficial in estimating safe operating times, but firefighters are also getting burned in fire environments that are thought to be routine exposures. The current study explored the thermal response of three-layer firefighter protective ensembles exposed to a majority convective, low-level heat flux in an oven. Through experimentation, the temperature of a copper calorimeter simulating skin beneath two different protective ensembles were measured while exposed to temperatures of 100°C, 150°C, 200°C, 250°C, and 300°C. The time for the copper calorimeter to reach a temperature of 55°C (the temperature a second-degree burn has the potential to occur to human skin) was recorded and compared to currently accepted thermal operating time limits for firefighters. Results show that once exposure reached above 100°C the time for a potential burn injury to occur fell below the predicted safe operational time for firefighters of 15–20 minutes when the PPE was in contact with the copper disk. The time to potential burn injury and test temperature exhibited an exponentially decaying relationship which is expected to continue as temperatures increase beyond those tested in the current study. Although consisting of different layers of material, both types of protective ensembles tested responded similarly and demonstrated no significant differences in time to potential burn injury at every temperature. Additional tests were conducted in the oven with an air gap placed below the protective ensemble as well as using the original test set up with a mostly radiative heat source to compare results and evaluate different exposures and conditions for future experimentation.Item Influence of the Air Gap in Firefighter Personal Protective Equipment on Skin Temperature in Pre-Flashover Thermal Exposures(2022) Ahmad, Shaheer; Milke, James A; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Exposure to pre-flashover thermal conditions is typically considered as routine for many structural firefighters, and these low level thermal exposures pose a threat of burn injury. Skin burns occur as a result of prolonged exposure within these environments, and this hazard must be addressed to reduce the number of firefighters that fall victim to thermal injury. The incorporation of an air gap within firefighter personal protective equipment (PPE) was explored in this work to gain an understanding of the influence of the air gap on skin temperature in pre-flashover thermal exposures. The relationship between the air gap size and skin temperature was investigated both through experimental and numerical means. Experimental testing was conducted to measure the temperatures at a representative skin layer positioned underneath firefighter PPE with an incorporated air gap subject to thermal exposures consistent with pre-flashover conditions. Material property testing was conducted for the same PPE-air gap assembly and the effective thermal properties for the bulk assembly were input into a computational model constructed with Fire Dynamics Simulator (FDS) to predict the temperatures at the equivalent skin position. The results show that the presence of an air gap within firefighter PPE prolongs the time to critical skin temperatures, and reduces the maximum temperatures reached at the skin surface. As the air gap thickness increases, the time to burn injury increases and the maximum temperatures at the skin decrease for both thermal exposures. These findings fundamentally suggest that the larger the air gap, the more thermal insulation is provided for the firefighter. Based on comparisons of the conduction-driven model with the experimental temperature data, the model was demonstrated to be accurate to within 15% of the experiments in the prediction of burn injury times for low heat flux exposures and small air gap sizes. The agreement of the model also confirms that the heat transfer is conduction-dominated for air gap sizes leading up to 6.35 mm, and transitions to alternative modes of heat transfer among larger air gap sizes.Item Prototype Design for Thermoacoustic Flashover Detector(2012) Buda-Ortins, Krystyna Eva; Sunderland, Peter; diMarzo, Marino; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The thermoacoustic flashover detector integrates the phenomenon of thermoacoustics into a fire fighting application. This report presents the prototype design for the thermoacoustic flashover detector to ultimately be implemented in a firefighter's gear. Upon increases in compartment fire heat flux and temperature corresponding to the onset of flashover, the device will produce a loud warning tone to alert the firefighter that flashover is impending. This is critical because post-flashover, the fire transitions to an untenable environment for a firefighter, as well as compromised structural integrity of the building. The current design produces a tone at 115 dB at about 500 Hz upon heating from an external band heater and cooling via an ice/water bath. At 38 mm from the device, this sound level is louder than the 85 dB from fire alarms and distinct from the 3000 Hz tone of smoke detectors. The minimum power input to the device for sound onset is 44 Watts, corresponding to a temperature difference of 150 degrees Celsius at a mean temperature of 225 degrees Celsius across a 2 cm long porous steel wool stack. The temperatures at the hot and cold ends of the stack are 300 and 150 degrees Celsius respectively, which is achieved with a response time of ~100 seconds. The sound is sustained as long as there is a minimum power input of 31 Watts. Although the measurement uncertainties are estimated at 10 degrees Celsius for the temperatures and 5 Watts for the power input, this design provides a foundation for future improvement and quantification of the device. The mechanisms of the thermoacoustics at work and the materials selected for the prototype are presented. Different power level inputs to the device are analyzed and temperatures for operation are determined. Suggestions for future optimization and integration of the device into firefighters' gear are presented.