Fire Protection Engineering Theses and Dissertations

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    (2023) Roche, Thomas William; Raffan-Montoya, Fernando; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The fire hazard associated with fabrics threatens everyone’s safety, and the current standards used to reduce those hazards are expensive and time-consuming. Fabrics are a key component in clothing, upholstery, and carpentry and are present in nearly every built environment. The inherent flammability of fabrics leads to the application of flame-retardant treatments on nearly all commercial fabric products. Recently, environmental, economic and performance concerns have driven research to develop new flame retardants across a variety of materials. The military industry in particular has focused recent research efforts on flame retardant treatments for fabrics, given the challenging environments that military uniforms must endure. Current methods for testing performance of novel flame retardants, such as the Cone Calorimeter and Microscale Combustion Calorimeter can be prohibitively expensive or only provide a limited understanding of flame-retardant action. Fabrics present additional testing challenges due to their low density and thickness, effectively reducing the amount of fuel available for testing. A novel apparatus, the Milligram-scale Flame Calorimeter (MFC), has been used to test flame retardants in polymeric materials, successfully capturing gas-phase activity and with favorable comparison to Cone Calorimeter results. This study aims to expand the use of the MFC to the testing of fabrics and flame-retardant treated fabrics. Optimization tests were run to find the optimal number of fabric layers and best method for preparing samples for use in MFC. Subsequently, cotton fabrics (untreated and treated with phosphoric acid), as well as Nylon fabrics (untreated and treated with tannic acid) were characterized with MFC, and results were compared to those from the Microscale Combustion Calorimeter and Cone Calorimeter. The MFC showed similar trends in the onset of ignition, peak heat release rate, average heat release rate, char yield, and heat of combustion for the untreated fabrics with the Cone Calorimeter and Microscale Combustion Calorimeter results. The results for the flame-retarded fabrics are inconclusive and require additional testing, though the observations of the condensed-phase and gas-phase activity for the MFC samples does provide important insights on how the mechanism for the flame retardants operate.
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    (2023) Zhang, Zilin; Milke, James A.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Crowds with densities higher than 2 persons/m2 can be defined as high-density crowds. High-density crowds presenting in daily life like concerts and sports events can lead to serious people and property loss. This research work focuses on developing a new speed-density relationship for high-density crowds. The applicability of the new speed-density relationship is tested in Pathfinder, an agent-based evacuation simulation software developed by Thunderhead Engineering, to determine the impact of updating such data on the model's performance. This research also discusses several parameters and functions in Pathfinder including acceleration time and reduction factor to help model high-density crowds.Previous work is available for analyzing crowds with densities lower than 3 persons/m2. However, densities as high as 9 persons/m2 are common in many high-density crowd scenarios. The disparity between previous work and real-world situations presents a challenge for engineers to understand the crowd dynamics of high-density crowds. Developing evacuation models to predict the behavior of high-density crowds is crucial to improving the predictive ability of crowd simulation. By doing so, it helps to reduce the number of casualties in future emergencies. Real-world footage videos are analyzed in this research. With the open-source experimental footage videos provided by Jülich, a national research institution, a new speed-density curve is summarized by collecting and analyzing data from the videos. The assessment of the applicability of the new speed-density in Pathfinder focuses on four aspects: evacuation time, flow density, flow velocity, and occupants’ arrangement. Per case examined, by applying the new speed-density curve, the predicted evacuation time from Pathfinder simulation is improved from 12.6% to within 4.9% of the experimental video time. The predicted flow density is improved from 6.2% to within 0.7% of the average video density. The predicted flow velocity is improved from 25.9% to within 3.3% of the average video velocity. At the same time, it is observed that occupants in the model behave more realistically.
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    (2023) Braddock, Sofia Le; Milke, James A; Trouve, Arnaud; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The 2020 National Defense Authorization Act (NDAA) prohibition of PFAS-containing AFFF fire protection systems by 2024 has motivated the U.S. Department of Defense to study other alternatives. In this study, the current low-expansion AFFF foam fire suppression systems with trenches layout in NAVFAC facilities are modeled as water-based systems to determine the scale, coverage, and extinguishment times that can be expected from such systems. A reduced spacing of the trenches is then simulated to determine how spacing of the floor nozzles affects fire suppression and control. Additionally, a model of a previously identified floor-level low-pressure water mist nozzle with the incorporation of trenches is studied to validate its possibility of being a replacement option for the current NAVFAC systems. Each simulation consists of three components: fire model, sprinkler/water mist model, and extinction model. Each model is evaluated separately before inputting into the final simulations to determine the most accurate representation and minimize uncertainties. The final simulations with sprinkler nozzles show successful extinguishment up to 23 MW and better performance at earlier activation time and in setups with the current trench spacing. Little to no difference is observed between the two fuel spill fire scenarios at the same activation time and trench spacing. On the other hand, the low-pressure water mist systems do not meet adequate performance in the final hangar simulations.
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    (2023) Lauterbach, Alec; Stoliarov, Stanislov I; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In recent decades, the intensity of wildfires worldwide has escalated, leading to a rise in the destruction of structures and loss of lives within the Wildland-Urban Interface (WUI). Firebrands are small fragments of ignited vegetation or structural material that are carried by the plume of a wildfire, traveling in advance of the main fire front. Firebrand exposure has been recognized as the primary mechanism for the propagation of wildfires as well as a source of ignition of structural elements. However, this complex ignition process of structural elements in the WUI has yet to be fully understood. The ignition and combustion characteristics of a thermoplastic-wood composite (Trex) and Pressure Treated Wood (PTW), two frequently used WUI decking materials, when exposed to glowing firebrand piles were studied using a bench scale wind tunnel. An inert insulation material, ii Kaowool PM, was also used as a deposition substrate to quantify the heat feedback and combustion characteristics of solely the firebrand pile. Firebrand pile densities of 0.16 g cm-2 and 0.06 g cm-2 were deposited on each substrate in rectangular 10 cm x 5 cm orientations and exposed to air flow velocities of 0.9 m s-1, 1.4 m s-1, 2.4 m s-1, and 2.7 m s-1. Infrared camera measurements were used to determine the back surface temperatures of Kaowool PM tests. Using DSLR cameras, surface ignitions of the decking material in front of the firebrand pile (preleading zone ignition events), ignitions on top of the firebrand pile (pile ignition events), and surface ignitions of the decking material behind the firebrand pile (downstream ignition events) were visually quantified via their probability of ignition, time to ignition, and burn duration at each testing condition. A gas analyzer was used to compare combustion characteristics of Trex, PTW, and Kaowool PM tests through heat release rate (HRR) and modified combustion efficiency (MCE). Peak back surface temperatures of the firebrand pile were found to increase with increased air flow up to 2.4 m s-1, and then plateau. The same trend was observed for the ignition probabilities of preleading zone and pile ignition events. The probability of downstream ignition events increased with increasing air flow velocity. Peak HRR increased with increasing air flow velocity. Trex exhibited significantly less smoldering combustion than PTW yet was prone to more intense flaming combustion. When the rectangular 5 cm x 10 cm firebrand pile (10 cm edge facing the airflow), of which the majority of tests were conducted on, was rotated 90 degrees so that the 5 cm edge faced the airflow, the result was a significant decrease in the probability of ignition for both Trex and PTW, along with notable reductions in their HRR and MCE profiles.
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    Predicting the Ignition Time and Burning Rate of Thermoplastics in the Cone Calorimeter
    (1995) Hopkins, Donald Jr.; Quintiere, James G.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, MD)
    Ignition and burning rate data are developed for Nylon 6/6, Polyethylene, and Polypropylene in a Cone Calorimeter heating assembly. The objective is to examine a testing protocol that leads to the prediction of ignition and burning rate for thermoplastics from Cone data. The flame heat flux is not measured, but is inferred from Cone data. The constancy of the flame heat flux for thermoplastics in the Cone calorimeter is due to the geometry of the flame. The burning rate model is shown to yield good accuracy in comparison to measured transient values. Ignition and burning rate data are developed for Redwood and Red Oak in a Cone Calorimeter heating assembly. Measurements of the flame plus external heat flux are presented. The data is intended to be used for future work to develop a testing protocol and burning rate model for charring materials.
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    Experimental Study of Heat Transfer Through Window Assemblies Under External Heat Flux
    (2023) Schrader, Rebekah; Ni, Shuna; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Structure hardening is a key strategy to help mitigate building destruction during wildland-urban interface (WUI) fires. While hardening all exterior components of a structure is important, windows have specifically been identified as a vulnerable part of a building. The purpose of this study is to characterize the heat transfer through single- and double-pane windows constructed of plain and tempered glass. Double-pane windows with and without low-emissivity coatings and with either air or argon-filled gaps are included in this study. Small-scale experiments were performed on 23 cm x 23~cm windows exposed to a radiant panel producing centerpoint heat fluxes of 10, 20, 30, 40, and 50 kW/m2 to the exposed side of the glass. Each experimental condition was tested in triplicate. Total and radiative heat flux was measured 5.1 cm behind the unexposed side of the glass at the center of the window. Additionally, total heat flux was measured in the bottom corner of the window to characterize the difference in uniformity of heat transfer across the plane of the window. Surface temperatures on the exposed and unexposed side of the glass were measured in various locations using type K inconel-sheathed thermocouples. Tests lasted for either 20 minutes, until glass failure, or until frame failure. Times to glass crack and failure were recorded. Results showed that double-pane windows reduce heat transfer through a window compared to single-pane windows (13-43% and 39-60% of incident measured, respectively); additionally, the application of a low-emissivity coating is effective (heat fluxes measured were 5-17% of incident). Plain vs. tempered glass and air vs. argon-filled pane gaps do not yield statistically different results in heat flux measured behind the window. Temperatures were not uniform across the plane of the glass on both the exposed and unexposed sides. Finally, tempered glass had better survivability than plain glass (22/23 and 0/16 survived at incident heat fluxes up to 30 kW/m2, respectively), and double-pane argon-filled windows consistently survived longer than double-pane air-filled windows.
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    (2023) Lee, Kelliann Ross; Milke, James; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The U.S. Congress has mandated the phase out of foam suppression systems for the protection of aircraft hangars due to the toxic composition of fluorine foams. Water mist is one alternative proposed to replace foam systems. This study examines high pressure water mist systems in a ceiling configuration and a floor and ceiling combination layout on three fire scenarios in FDS. This work is split into three models- the fire model, the water mist model, and the extinction and evaporation model before combining each component in a final hangar configuration. Within the fuel model, three radiation modeling options were tested, and each fire was constructed. The water mist model tested the length scales of the jet stream and associated grid resolution. The evaporation model was verified to ensure accurate heat transfer between Lagrangian particles and the gas phase. Simulations in the final hangar configuration showed the high-pressure water mist systems were able to provide fire control, performing better at an earlier activation time. The floor and ceiling combination layout provided faster control compared to the ceiling nozzle only layout. A wind condition was added in a second round of testing, but minimally impacted the performance of the systems.
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    (2023) Bors, Jeffrey; Trouve, Arnaud C; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In computational fluid dynamics (CFD) fire models, sprinkler sprays are represented in complex numerical simulations using Lagrangian particles. These CFD sprays are typically characterized using a combination of experimental data, literature correlations, and estimation. The Spatially-Resolved Spray Scanning System (4S) machine provides high resolution data to characterize sprays for use in CFD analysis, however a quantitative analysis on the effect of this high resolution data with FDS in realistic fire scenarios has not been completed before. 4S spray data is analyzed and compared to a basic spray estimated from literature correlations with and without the presence of fire to analyze trends. In all environments, the basic nozzle overestimated water flux closer to the center of the nozzle and underestimated water flux farther from the center. Differences between the basic and 4S nozzle ranged from 1% to 240% in the enclosure fire scenario. Investigation into the differences showed the polar water distribution to be the most impactful parameter provided by the 4S. Local azimuthal trends were shown to be significant, but non-impactful in the enclosure fire simulation. Global azimuthal trends were apparent but not significant.
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    (2022) Hussain, Zishanul Haque; Trouve, Arnaud; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Fire Dynamic Simulator (FDS) is a computational fluid dynamics (CFD) model of firedrivenfluid flow. It was first released publicly in February 2000. Using SmokeView or Pyrosim to view the results of FDS simulations provides a powerful non-immersive virtual reality experience. It can be used in fire engineering, fire safety training, and fire investigation. By providing a more engaging and interactive user experience, nonimmersive VR can help improve understanding and develop effective fire safety and prevention strategies. On the other hand, FDS is a powerful tool for modeling the physics of fire behavior in buildings and other structures. It has been shown to produce accurate descriptions of fire behavior under a variety of different conditions. This study touches on very divergent, yet very critical, aspects of the applications of FDS. First, generating life-like simulations of fire and smoke characterized by different growth rates and surroundings (a non-immersive virtual reality application). Human behaviour experiments at Morgan State University will use the simulation videos to assess the accuracy of human estimates of fire growth rates and understand how situational factors impact human response. The second part of the study focuses on the Lagrangian particle representation of water droplets in FDS simulations of fire suppression. This study id is going to look at the fire suppression model in which fire suppression is defined by surface wetting or the mass of water falling in the fire surface. The Lagrangian liquid water droplets tracked by FDS represent a larger number of actual droplets. The number of ‘super drops’ can affect the accuracy of the simulations. The particle insertion rate has a default value and controls the mass of the 'super drop'. FDS allows altering the particle insertion rate and hence the mass of the 'super drop. The goal is to find out how changing particle injection rate and mesh grid size impacts the accuracy of the simulation of water sprays.
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    (2022) Tan, Genevieve Claire; Milke, James A.; Trouve, Arnaud; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Large fires in humanitarian settlements lead to enormous losses in material, time, and resources that organizations allocate toward supporting refugee camps and displaced persons. In the absence of full-scale shelter fire experiments in humanitarian settlements, a combination of video analysis and fire modeling can be used to estimate burning characteristics of the shelter fire. A MATLAB-based image binarization method is developed to measure the flame height and structure loss over the course of fire development in footage from a shelter burn test conducted in Cox’s Bazar, Bangladesh. The conditions of the shelter fire are recreated in Fire Dynamics Simulator (FDS). Diagnostics in the FDS models provide estimates for the flame height, heat release rate, heat flux, and radiant integrated intensity in and around the shelter. The FDS models exhibit a 10-25 second delay in matching key events in the fire development timeline of the original shelter fire. Otherwise, measurements from the FDS simulations show good agreement to measurements from image processing. Based on results from image processing and FDS models, the steady burning HRR is approximately 900 kW for a shelter fire with a flame height range of approximately 4.1-4.5 m.
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    (2022) Roy, Shuvam; Stoliarov, Stanislav; Raffan-Montoya, Fernando; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Standard bench scale fire apparatuses are useful tools to perform repeatable and reproducible firetests that acquire key fire properties, such as heat release rate and time to ignition, for materials in a cost-effective manner. The Fire Propagation Apparatus (FPA) is one of the only standard bench scale apparatuses that has the ability to acquire these key fire properties in a controlled environment setting. However, the design of the apparatus is quite complex. In this work, the exhaust and gas sampling system designs were redesigned and constructed to increase modularity and manufacturability, adapt to the University of Maryland’s Department of Fire Protection Engineering laboratory settings, and provide greater ease for the end user operations. After the construction of the FPA systems, tests were conducted to verify the accuracy of the measurement devices. Equations for the calculation of heat release rate from FPA sensor data were derived and used for a series of combustion experiments. These equations were compared to the ones provided in the standard to gain insight on their systematic differences.
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    (2022) Kim, Minhyeng; Sunderland, Peter B.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    An improved understanding of cool diffusion flames could lead to improved engines. These flames are investigated here using a spherical porous burner with gaseous fuels in the microgravity environment of the International Space Station. Normal and inverse flames burning ethane, propane, and n-butane were explored with various fuel and oxygen concentrations, pressures, and flow rates. The diagnostics included an intensified video camera, radiometers, thin-filament pyrometry, and thermocouples. Spherical cool diffusion flames, transitioned from hot flames, burning gases were observed for the first time. However, these cool flames were not readily produced and were only obtained for normal n-butane flames at 2 bar with an ambient oxygen mole fraction of 0.39. The sizes of hot and cool diffusion flames were investigated with the intensified camera images. The hot flames that spawned the cool flames were 2.6 times as large. An analytical model is presented that combines previous models for steady droplet burning and the partial-burning regime for cool diffusion flames. The results identify the importance of burner temperature on the behavior of these cool flames. They also indicate that the observed cool flames reside in rich regions near a mixture fraction of 0.53.
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    (2022) Bellamy, Grayson; Stoliarov, Stanislav I; McKinnon, Mark B; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Previously developed, the Controlled Atmosphere Pyrolysis Apparatus (CAPA) was designed to address the needs of a well-characterized gasification apparatus from which material properties could be derived. Although the data from CAPA has been well-validated through modeling and other various means, only a single functional and published version of the apparatus exists which hinders widespread acceptance. Additional concerns and questions about the design remain which warrants further improvement and investigation. In this work, elements of CAPA are revisited, redesigned, and improved to provide a more defined environment for bench-scale material evaluation. Existing geometrical constraints were maintained to allow for a direct comparison to previous work and confirm previous characterizations. In pursuit of these goals, several improvements were made. Implementation of an integrally water-cooled chamber was accomplished through additive manufacturing, allowing chamber temperatures to remain steady throughout the duration of a test, reducing additional radiant heat flux to the sample. Measurement resolution was increased with an upgraded thermal imaging camera, mass balance, and data acquisition system. Full analysis of the gas temperatures, chamber temperatures, oxygen concentration, and overall thermal environment was performed to replicate previous results and provide quantitative information for use in a pyrolysis modeling. Characterization experiments confirmed that heat flux profiles and gas temperatures are within the experimental uncertainty of both apparatuses. Chamber temperatures were reduced, providing for more clear boundary conditions and simplified modeling. Experimental results of this improved version of CAPA were compared against previous experiments conducted on poly(methyl methacrylate) (PMMA) and oriented strand board (OSB). Mass loss rate and surface temperature data were comparable indicating the apparatus performs as intended. Several problems and concerns were identified in this process for further study. This work provides further confirmation of the usefulness and accuracy of CAPA for use in analyzing the thermal decomposition of materials.
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    Firefighter Portable Radio Carrying Methods: Pocket or Strap?
    (2022) Brondum, Nicholas Joseph; Milke, James A; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Firefighters rely on their portable radios daily for communication. This project examines firefighter portable radios and their carrying methods. Carrying methods such as radio pockets sewn into turnout gear and radio straps are examined with respect to carrying utility, thermal protection, and decontamination ability. Information was gleaned from several firefighter line of duty death and “near miss” reports, personal interviews, empirical testing, computational fire modeling, and previous studies. Tests were conducted with radios carried in radio straps both above and below the turnout coat, as well as in the radio pocket. Radios were exposed to a radiant heat flux determined from computational fire modeling via a radiant panel until the test radio was either unable to transmit or receive messages from another radio. From this analysis, it is determined that wearing a portable radio in a radio strap under a turnout coat is the most efficient and safest way to carry a radio.
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    (2022) Dietz, Emily; Stoliarov, Stanislav I; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Some of the most devastating consequences of the increasing occurrence of large wildfires throughout the world are the acres of land burned and the number of structures lost. Firebrand exposure has been identified as one of the main mechanisms of how wildfires spread as well as an ignition source for structural components. A bench-scale experimental procedure was developed to study the ignition process of Western Red Cedar (WRC) and Oriented Strand Board (OSB), two common materials used in the construction of outdoor decks. To study the combustion process of these materials, they were loaded into a wind tunnel and exposed to a constant wind velocity of 1.4 m s-1, 2.4 m s-1, or 2.7 m s-1 and a glowing firebrand pile coverage density of either 0.06 g cm-2 or 0.16 g cm-2. All tests were also conducted using Kaowool PM, an inert ceramic fiberboard, in order to quantify the heat feedback of the isolated firebrand pile as well as differentiate the contributions of WRC and OSB to the combustion process from that of the firebrand pile. Surface ignitions on the combustible materials were determined visually and characterized by time to ignition after deposition, burn duration, and location of ignition events. Back surface temperature profiles were collected using an infrared camera. Results from gas analyzer measurements were used to compare the combustion characteristics of the WRC, OSB, and Kaowool PM under the same conditions through heat release rate (HRR) and modified combustion efficiency (MCE) profiles. Additional tests were conducted under a single airflow of 2.4 m s-1 and firebrand pile coverage density of 0.16 g cm-2 yet rotated the orientation of firebrand deposition onto the board by 90 degrees, doubling the leading edge length of the firebrand pile. A series of tests also varied the airflow in the tunnel for a comparison between the surface ignition characteristics and the temperature profiles of the firebrand pile between continuous and intermittent wind exposure for a 2.7 m s-1 airflow and a 0.16 g cm-2 firebrand pile coverage density. Results included a higher probability of ignition on WRC than OSB under all continuous wind conditions, higher peak temperatures achieved with an increasing airflow up to 2.4 m s-1, and combination smoldering-flaming mode of combustion for the system, whether that be the firebrand pile alone or the firebrand pile deposited onto WRC or OSB. It was also found that changing the firebrand pile deposition orientation leading edge length by a factor of two doubled the number of surface ignitions observed on both WRC and OSB. Compared to the continuous wind condition, gusting the airflow velocity caused an increase in the number of ignitions by a factor of 14 on WRC and 19 on OSB, yet each saw a decrease in the burn duration by a factor of at least 4.
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    (2022) Leahy, James Ryan O; Sunderland, Peter B; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Due to the increased concerns about climate change, multiple states including California havestarted to pass legislation that phases out high global warming potential (GWP) refrigerants in HVAC and refrigeration systems. The likely replacements are A2L refrigerant which have lower GWP and are mildly flammable. This will require area monitoring leak detection systems for all future applications of these refrigerants. These detection systems preferably need to operate continuously for up to 15 years. The UL 60335-2-40 (2019) standard defines the sensor response time which must alarm within 10 seconds of exposure to 100% of the refrigerant’s LFL. Development of sensors capable of meeting the UL 60335-2-40 standard has been slow with many different types of gas sensing technologies being used. One of these technologies that was identified as a potential candidate was non-dispersive infrared (NDIR). A sensor not yet available commercially was able to be obtained to test its response to A2L refrigerants R-32 and R-454B according to the UL 60335-2-40 standard. Three other competing sensing technologies were also obtained to compare the performance of other sensors about to hit the market. These sensors were characterized by their linearity to varying concentrations of A2L refrigerant, response time, and to contamination. All the tested sensors were able to meet the 10 second requirement for response time. However, all but the NDIR sensor experienced a change in output when exposed to a list of prescribed contaminants by the UL 60335-2-40 standard. After the contamination, the NDIR sensor showed no change in its output indicating it experienced no poisoning effect. The NDIR sensor was deemed to have the optimal performance out of the sensing technologies. Long term exposure, exposure to contaminants and refrigerant at the same time, and service lifetime are still concerns.
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    Feasibility Analysis of Coupling FDS Modeling with Machine Learning for Situational Awareness in Aircraft Hangars
    (2022) Davis, Alison Marie; Milke, James A; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Situational awareness is a critical factor in maintaining the safety of firefighters and can be largely improved in buildings using distributed sensors that provide real-time data. A two-phase approach is used to increase situational awareness in aircraft hangars. Phase I consists of modeling a hangar with an open door in Fire Dynamics Simulator (FDS), with a high density of smoke, temperature, CO and CO2 sensors located at the ceiling. Fuels of interest including Douglas fir, polyethylene, paper, JP-8, and propane are modeled in six potential fire locations, with five locations along the centerline of the hangar and one in the corner of the hangar. Additionally, wind and beams at the ceiling are added to the simulation to determine the impact on the products of combustion that the sensors pick up. Phase II uses the data acquired from the FDS simulations to inform and build machine learning models that utilize supervised learning techniques to identify the location of the fire, the magnitude of the fire and the composition of the fuel that is burning. It is determined that temperature and smoke are the key products of combustion needed for these analyses. The location of the fire is identified within a circular area with a 5 m radius by using temperature measurements, thus reducing the amount of input data needed for the machine learning models. The magnitude of the fire is predicted using temperature as inputs to a heat release rate (HRR) model using a fully connected, three-layer, feed forward neural network. The composition of the fuel is predicted using a linear support vector machine that supports multi-class classification, using products of temperature and smoke obscuration as inputs. The location model is 80% accurate, the HRR model is 85% accurate and the fuel composition model varies between 62% and 91% accuracy depending on the classification goals. These results prove the feasibility of machine learning applications in an aircraft hangar setting.
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    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.
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    (2022) Tlemsani, Mahdi; Sunderland, Peter B; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Wildfire, especially along the Wildland Urban Interface (WUI), presents a large threatto life and property globally. Firebrands can increase the size and spread of wildfires rapidly. More than half of spot fires and WUI fires are caused by firebrands. Firebrand generation, transport, and morphology has been studied in recent literature, but few papers have reported firebrand temperatures, even fewer on groups of firebrands across varying configurations. Those that have reported temperatures have typically relied on expensive IR and thermocouple data that may not be as accurate at determining temperature or emissivity. Color camera pyrometry presents a high resolution alternative to previous pyrometry methods and can be done using a cheap color camera, and with certain techniques can derive temperature independent of emissivity. This research builds on previous color camera pyrometry, automating the process to allow for large datasets to be analyzed as opposed to single images. Two-color, grayscale, and hybrid pyrometry [20] were used to recreate pyrometry results of previous literature. Similar average single firebrand temperatures in the range of 900-950C were reported. A novel Pixel-by-Pixel hybrid pyrometry was developed to incorporate more data into established hybrid pyrometry methods. This method introduced large amounts of noise into the temperature results, making them unreliable. Additionally, a method was developed for determining the temperature of 8-gram ember piles at various wind speeds of 1.4, 2.4, and 2.7m/s through a borosilicate glass window. Modified grayscale temperatures assuming constant emissivity were used for these experiments and were fit to firebrand temperature data from Kim and Sunderland [20]. A total of 720 ember pile images were analyzed in the final dataset at an effective emissivity of 0.76. Peak ember pile average temperatures ranged from 700-900C. Normalized temperature (T /Tmean) PDFs were produced. Data was approximated as a normal distribution with mean of 1 and standard deviation ranging from 0.048 - 0.057.
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    (2022) Lee, Adam; Milke, James A; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This research project aims to identify room configuration conditions in which FDS, a CFD model, and CFAST, a zone model, may differ in detector activation time. A total of four configurations, with varying aspect ratios, were explored. Additionally, a range of four ceiling heights were also modeled. Furthermore, a total of three statistically significant models were developed to relate the differences between detection times within CFAST and FDS. It was found that FDS and CFAST discrepancies were a result of the compartment volume to doorway area ratios. Larger volumes compared to the doorway area resulted in better agreement between FDS and CFAST. Additionally, for larger ceilings in FDS, larger variability in activation times were present. Furthermore, for higher ceilings, FDSs’ ability to account for thermal buoyancy within the smoke plume resulted in quicker activation within FDS.