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1.2: Changes in the Fire Environment

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    Changes in the Fire Environment

    Over the past several decades, homes have undergone a dramatic change in the way they are built, the materials they are built with, and how they are furnished. These changes have made the fire environment that firefighters work in significantly more dangerous and require that firefighters have a much better understanding of fire behavior than previous generations needed to operate safely and successfully in the fire environment.

    Modern Furnishings

    The most significant change in the fire environment that today’s firefighters face is the introduction of polymers such as foams and plastics. Polymers are synthetic materials primarily made from natural gas and petroleum. What makes these materials so different is that they are capable of burning faster and hotter than the natural materials, such as wood and cotton, that many products inside the home used to be made of (legacy fuels). Take a look at the home furnishings comparison video to see how the modern furnishings compare to these legacy furnishings.

    Home Furnishings Comparison

    Consider how modern furnishings made of synthetic materials compare to legacy furnishings such as wood and cotton impact the fire environment.

    Video: 2020 FSRI Home Furnishings Comparison (Natural vs. Synthetic) by Fire Safety Research Institutes, 2020. Used according to FSRI Terms of Use.

    Larger Spaces

    Another change that has had an impact on the fire environment is the size of homes and the spaces within homes. Homes today have increased dramatically in size. In fact, according to research from the UL Fire Safety Research Institute, homes in 1973 averaged just 1600 square feet while in 2008 they averaged 2500 square feet.1 In addition to larger home sizes, new building materials such as engineered supports have allowed significantly more open floor plans. With less compartmentalization, these open floor plans allow fire, smoke and heat to move more freely throughout the structure, resulting in fire consuming more fuel, and involving the structure itself in a shorter timeline.

    Lighter Weight Building Materials

    As mentioned above, many components in modern structures utilize engineered materials. For example, rather than using traditional boards such as a 2x10 to support a floor, modern homes utilize engineered I-beams made from small-dimension wood and oriented strand board as seen below. While these products have equal or even greater load-bearing strength, they have significantly faster failure rates when exposed to fire. In fact, according to the National Institute of Technology research, houses built with legacy materials collapse after 35-48 minutes exposed to fire, while homes built with lightweight materials risk collapse in just 3-5 minutes.

    Lightweight floor joist
    Figure \(\PageIndex{1}\): Floor trusses.
    Copyright: "Floor Trusses" by ArmchairBuilder.com, licensed under CC BY 2.0.
    Lightweight engineered floor joist
    Figure \(\PageIndex{2}\): Lightweight engineered floor truss
    Copyright: Original photograph by Robert Smith, licensed under CC BY-NC 4.0.

    Smaller Lots

    Building lots have also decreased in size in the past 50 years. In 1976, the average lot size was over 10,000 square feet.2 However, in 2024, the average lot was just 8500 square feet and 40% of homes were built on lots less than 7000 square feet.3 Larger homes and smaller lots mean that the risk of fire moving from a single structure to multiple structures is more likely, and firefighters have less room to operate around homes.

    Void Spaces

    Modern engineering has also allowed more complex designs. Today's homes emphasize visual appeal and often have complex roof designs to add character and uniqueness to homes. These designs result in uninhabitable spaces throughout the structure. These spaces can allow fire to spread into other parts of the structure, and create challenges for firefighters to access and extinguish fire in these spaces.

    Exterior of a modern home with complex roof design

    Figure \(\PageIndex{3}\): Modern home with complex roof design.
    Copyright: "Fancy new house in Northwest Austin" by rutlo, licensed under CC BY 2.0.

    New Technology

    The final factor that has changed the modern fire environment is the technology that is being incorporated into structures. Solar systems are becoming increasingly common on homes. In 2025, about 7% of homes had solar systems, nearly twice that in 2020, and by 2030, solar systems are expected to be present on more than 15% of homes.4

    Solar systems present several hazards to firefighters. First, the panels block access to roof spaces, increasing time to access fires in attic spaces, and reducing access points. Additionally, solar panels do not stop generating electricity. While these systems do have switches to disconnect the panels from the home, they will remain energized up to that switch, posing a potential electrocution hazard to firefighters. Finally, these systems typically have large battery systems in basements or mechanical rooms, presenting an electrical hazard as well as chemical hazards and possible metal fires. These batteries also pose a re-ignition hazard as well. In addition to solar panels, wind turbines are also increasing in popularity and present similar challenges to firefighters.

    Solar panel installation on roof of modern home
    Figure \(\PageIndex{4}\): Photovoltaic panels on modern home.
    Copyright: "180511-F-BO262-1009" by Roland Balik, U.S. Air Force. Public domain.

    References

    1. Kerber, S. (2013, August). Part 2: The modern fire environment [Video]. UL Fire Safety Research Institute and National Institute of Standards and Technology. Available from https://www.youtube.com/watch?v=FR4FZUkzKHM.

    2. Kerber, S. (2013, August). Part 2: The modern fire environment [Video]. UL Fire Safety Research Institute and National Institute of Standards and Technology. Available from https://www.youtube.com/watch?v=FR4FZUkzKHM.

    3. Siniavskaia, N. (2025, July 1). Shrinking lots, spec building: New norm? Eye on Housing. https://eyeonhousing.org/2025/07/shrinking-lots-spec-building-new-norm/

    4. Patel, J. (2025, September 22). Solar home panels in 2026: How many American households use them? SolarCC. https://solarcc.com/solar-home-panels/

    This page titled 1.2: Changes in the Fire Environment was last modified on Fri, 21 Aug 2026 02:07:56 GMT and is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Robert Smith.