Partnering with ISFSI to research safer ways to fight basement fires.

Understanding and Fighting Basement Fires

Partnering with ISFSI to research safer ways to fight basement fires.
  • Overview
  • Findings
  • Updates
  • Resources


Many firefighters have been injured or died while trying to extinguish a basement fire or a fire on a level below them. A collaborative effort between UL’s Fire Safety Research Institute (FSRI) and the International Society of Fire Service Instructors (ISFSI), the Understanding and Fighting Basement Fires project (Basement Fires) seeks to reduce the high risk to firefighters by better understanding why these events occur and what firefighters can do to avoid injury. 

This study goes beyond past research by increasing the size of the basement and incorporating three different access conditions to the basement, with findings being incorporated into an ISFSI Training Program for firefighters. 

This project is supported with a Department of Homeland Security and Federal Emergency Management Agency Assistance to Firefighters Grant.


Previous FSRI research has shown that basement fires present a high risk to firefighters. This risk stems from unexpected floor collapse and high heat. There are indications that the tools firefighters have traditionally used to determine the structural integrity of the floor are of little value with lightweight construction. Prior experiments in small basements have indicated that the most effective method of fighting a basement fire may be on the exterior of the building.


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This study examined three different ventilation and access conditions to the basement: no exterior access to the basement, limited exterior access to the basement, and exterior access to the basement. 

A variety of fire nozzles and appliances were used to examine means of effectively flowing water into the basement through the floor above, through small side windows, and through basement level doorways. Each of these suppression methods provided a means of fighting the fire at its own level, without having to operate over the fire on an unrated wood floor assembly as well as remaining out of the exhaust portion of the basement fire flow in the basement stairway.

These experiments highlighted the importance of identifying a basement fire during size-up and choosing the appropriate tactics that coordinate ventilation with suppression. Additional ventilation to these ventilation-limited fires without suppression was shown to increase the size of the fire and increase the hazard to any occupants trapped in the structure.

Effective water application into the basement cooled the fire gases to prevent flashover, slowed the destruction of the structure, and reduced the hazard from fire throughout the structure.


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Published: January 1, 2016