Understanding and Fighting Basement Fires

The ISFSI & UL FSRI 2017 Joint Research Project

By Brian Kazmierzak and Dan Madrzykowski

Firefighters have always been taught that basement fires are one of the most dangerous fires to fight. They have been trained to operate above the fire and make their way down the throat of the fire to attack the fire on its own level. We understand from previous research that the floor systems on which we are walking or crawling fail quickly and without warning. Exposed wood-flooring systems do not maintain their structural integrity for long under fire conditions unless they are protected by drywall or a sprinkler system.

Since the double line-of-duty deaths (LODDs) on Cherry Road in Washington, D.C., in 1999, we have also been aware of  the “flow path” and its impact on firefighting, particularly in basement fires. What we must realize is that flow path didn’t first come about in 1999; we just became more aware of it then and, through technology, were able to recreate it and distribute simulations from the National Institute of Standards and Technology (NIST) for the fire service to study. This article provides an overview of the International Society of Fire Service Instructors (ISFSI) “Understanding and Fighting Basement Fires Project,” which includes a brief history of previous research, LODD basement fires, the research questions, and the tactical considerations developed as part of this research. In 2016, the ISFSI was awarded its most recent Assistance to Firefighters Grant Program’s Fire Prevention and Safety Research Grant. The study was funded to research basement fire attack tools and tactics and determine which are the most effective.   

The Study

The ISFSI developed a technical panel to guide the research to ensure that the end results would be beneficial and useful to the fire service. The panel included representatives from several sections of the International Association of Fire Chiefs (IAFC), the North American Fire Training Directors, the National Institute for Occupational Safety and Health (NIOSH), and from several fire departments that had suffered LODDs because of basement fires. The  ISFSI partnered with the Underwriters Laboratories (UL) Firefighter Safety Research Institute and the Delaware County (PA) Emergency Services Training Center to conduct the research.

The next step was to examine the previous research and fireground experience to understand the gaps in understanding basement fires. During the past 10 years, several floor-collapse studies have been conducted. In 2008, the UL Fire Safety Research Institute published its research findings on the structural stability of engineered lumber exposed to fire conditions.1 The experiments were conducted on a floor furnace.  The research demonstrated that “modern” engineered wood-floor assemblies failed faster than wood-floor assemblies with “legacy” designs. This study also pointed out that modern tools like thermal imaging cameras (TICs) had limited use in determining the condition of the floor assembly or the fire conditions under the floor. Further, the study questioned the use of the time-honored practice of “sounding the floor” to determine if it was safe to operate on the floor.       

In 2012, the  UL FSRI and NIST released a study on the examination of four types of flooring systems in a townhouse type of arrangement with a 720 square foot (67 square meter [m]) floor area and a 20 foot (6.1 m) span. These experiments examined the time to collapse for residential floor systems constructed with dimensional lumber, wood I-joists, parallel chord wood trusses, and lightweight steel C-channel. The results proved that any of the unprotected floor assemblies could collapse within the operational time frame of the fire department. This report also provided data that showed that current fireground practices of entering on the floor above the fire and working down to fire the basement would not provide the firefighter with the appropriate information to make decisions to provide a safe operating environment.2     

As a follow-up to UL’s floor furnace experiments, NIST conducted experiments in two-level wood structures with a 16 foot (4.8 m) span that supported the findings of the UL study on the value of gypsum board to protect the floor assembly and the challenges for TICs. Three TICs, each with a different type of sensor, were used to view and record the thermal conditions of the top of the floor assembly from the open doorway in the upper compartment. The times to the collapse of each floor were also noted. Given the insulating effects of the oriented strand board (OSB) and the floor coverings, the temperature increases or thermal signatures viewed by the TICs were small, given the fact that the ceiling temperatures below the OSB were in excess of 1,110°F (600°C).

These experiments further demonstrated that TICs alone cannot be relied on to determine the structural integrity of a wood-floor system. Therefore, it is critical for the fire service to review its practice of size-up and other fireground tactics needed to enable the location of the fire prior to conducting fire operations inside a building. This study also highlighted the relationship of increased ventilation to the growth of the fire in the lower level, which led to failure of the floor assemblies.

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