Evaluation of Ventilation-Controlled Fires in L-Shaped Training Props

Abstract

Investigations of recent firefighter line of duty deaths caused by rapid fire progression have highlighted a deficiency in firefighters’ understanding of how certain tactics affect the fire dynamics of ventilation-controlled fires. Many fires are in a ventilation-limited, decay state by the time firefighters arrive at the scene, meaning that introducing additional ventilation to the environment has the potential to cause rapid and intense fire growth. To more effectively teach firefighters about the potential effects of ventilation on a compartment fire, ventilation-controlled fires should be gener- ated during training. Safely creating such fires while maintaining compliance with NFPA 1403: Standard on Live-Fire Training Evolutions allows instructors to educate students on this important principle of fire dynamics in the training environment. Structures utilized for live-fire training have evolved from typical concrete burn buildings to now include smaller purpose-built props, like those constructed from steel shipping containers or wood and gypsum board. Such props have been embraced by organizations due to their cost-effectiveness and potential to improve fire behavior training. Obtaining a thorough understanding of the capa- bilities and limitations of such props is critical for instructors to convey accurate messages during training and properly prepare firefighters for scenarios they’ll encounter in the field. Experiments were conducted to quantify the fire environment in L-shaped props with different wall constructions. One prop had an interior wall lining of gypsum board over wood studs and fiberglass insulation. The two other props were constructed from metal shipping containers with corrugated steel walls; one had ceilings and walls comprised solely of the corrugated steel, while the other had ceilings and walls comprised of rolled steel sheeting over mineral wool insulation with the corrugated steel wall as its backing. Three fuel packages were compared between the props: one contained furnishings mainly composed of synthetic materials and foam plastics; another contained wooden pallets and straw; and the third contained wooden pallets, straw, and oriented strand board (OSB). A stochastic approach was used to compare data between replicate tests and quantify the repeatability of the different props and fuel packages, all of which were deemed sufficiently repeatable. Comparisons of data between the three props revealed that thermal conditions between experiments in the two metal props were indistinguishable, suggesting that the additional layer of insulation did not significantly alter the fire environment. Additionally, thermal conditions in the gypsum-lined prop were more severe than those in the metal props. The effects of ventilation changes on fire conditions were also analyzed across various prop and fuel load combinations. Lastly, the response of the thermal environment in each prop during interior suppression was evaluated, and the results implied that the thermal exposure to the firefighter was more severe in the metal props than the gypsum prop for a brief period following the start of suppression.