The number of structure fires has been cut in half over the past three decades, according to the National Fire Protection Association, but the ones that do happen can be deadly. Our research shows that fire can engulf a new home eight times faster than a house built 50 years ago, and study we conducted with the FDNY and NIST  found that firefighter deaths have grown by 67 percent in 30 years.

To give firefighters the researched information they need to be safe and effective, UL embarked on a two-year study to examine the hazards of basement fires involving various residential flooring systems. Aimed at improving firefighter safety, this project was a collaboration of several research organizations, product manufacturers and fire service representatives to examine hazards associated with residential flooring systems. The research team conducted experiments on several types of floor joists and with different ventilation, fuel load, span and protection methods.

In the first phase of experiments, researchers worked with Michigan State University’s structural engineering program and burned various materials in furnaces and then built two simulated basements to test how long different floor systems would last before collapsing. The team then built identical structures inside a laboratory and ran the same tests without environmental factors, such as wind.

Finally, they did full-scale burns, setting fire to two houses — one built in the 1940s and the other in the 1990s – to measure how long they burned before collapsing. In total, researchers recorded results during 17 full-scale fire experiments.

Overall, the researchers found floors are built differently today, with fewer supports and longer spans.  Such floors are very unstable during a basement fire and gave little warning of collapse. With that knowledge, firefighters may consider a different approach than the traditional attack used to fight house fires, and adjusting training may save lives.

To prevent basement fires in the first place, slow their spreading or help occupants escape quickly, UL followed up the physical experiments with a series of computer models that showed more detail about what happens as a basement fire spreads. This modeling, which was done with computational fluid dynamics (CFD) software, allows scientists to see details like temperature and air flow inside a burning building and map fire risks that come with different architectural features and ventilation systems. The results of these experiments will help building engineers and regulators set standards that improve safety for the people who live and work in buildings with basements.  


UL Research ­– Fire Modeling of Basement with Wood Ceiling