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Ask an Expert

Stephen Kerber

Director of the UL Firefighter Safety Research Institute

How do modern fires differ from traditional fires?

While the physics of fire development has not changed over time, the fire environment, or more specifically the single-family home, has evolved. Several factors — including home size, geometry, contents and construction materials — have changed significantly over the past 50 or more years. The average home is significantly larger, contains much more open space, is furnished with synthetic contents, and is constructed out of newer materials that are more energy efficient and value engineered. While many of these changes have produced desirable results, the modern home fire is able to propagate faster, result in an unsurvivable condition sooner, reduce the time to escape and reduce the time to structural failure.

How have the hazards of home fires changed over the past 30 years?

Home fires are much more hazardous to occupants and firefighters. Our research shows that home occupants would have significantly less time to escape today than 50 years ago. The number of residential fires has decreased significantly, by more than half, but that does not reduce the hazard should a fire occur.


The conditions that firefighters are going to be faced with today and into the future have been significantly impacted by the ever-changing fire environment. As society continues to make changes to building materials as a result of the desire to be environmentally conscious and to increase profit, the fire environment is going to continue to change. And if the current trends in the fire environment continue, it will not be in favor of firefighter safety. Therefore, it is important that firefighters study this new fire environment and its impact on their safety and tactics. The first component of this is understanding that the conditions they are arriving to are very different than they were several generations ago. The fire environment can change rapidly due to under-ventilated fire conditions, and floor systems can collapse quickly and with little warning. Additionally, operating conditions need to be constantly monitored to understand the impact of the tactics used and the potential need to change them. Ultimately, if the fire environment has changed, tactics need to change or be reevaluated to have the greatest opportunity to be most effective on today’s fires.


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