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50 Years of Fire Safety Advances

Wildland-urban interface fire loss mitigation (2020s)

NIST is a leader in researching fires at the wildland-urban interface.
NIST researchers have developed unique tools such as the NIST Dragon and the emberometer to study the spread of wildfire.
NIST has also developed strategies for reducing the hazards of wildfires and evacuation that have already been adopted by communities in California.

For millions of years, wildfires have been a natural and beneficial part of ecosystems. However, as the global human population has grown, so has the number of dwellings at the wildland-urban interface (WUI), which is the area where human development meets natural, undeveloped terrain. During the past 30 years, the spread of wildfires into built environments has escalated rapidly, leading to significant losses of property and lives.

About one-third of the housing units and more than 60,000 communities in the United States are currently at risk from WUI fires. Each year, these fires destroy thousands of structures and claim dozens of lives, with annual costs estimated in the hundreds of billions of dollars.

It’s important to study these fires to reduce the harm they cause. NIST investigates certain WUI fires after they happen to recreate the events of the disasters and gain insights into how they caused so much damage. NIST staff then conduct research focused on three key aspects: fire spread, protection of structures, and community protection.

Fire Spread

Fire spreads through the WUI via the flames and firebrands. Radiation from the flames travels through space (like the Sun heating the earth) and can ignite structures up to 100 meters (300 feet) away. Hot air from the flames helps spread the fire by convection (like you experience when you sit in front of an air vent in winter). Firebrands, also called embers, are small pieces of burning material emitted by flaming trees and wooden structures. They are a major but previously overlooked factor in WUI fire spread. When carried aloft on wind currents, they can descend and create new fires several kilometers ahead of the main fire.

NIST has applied its Fire Dynamics Simulator to predict the complex wildfire movement. These simulations have helped both with understanding fires that have already happened as well as planning for fires that might happen in the future. NIST and its partners have occasionally set carefully controlled wilderness fires to validate these simulations.

NIST is a leader in firebrand research. Its staff created the NIST Firebrand Generator, also known as the “NIST Dragon.” This device is an extremely useful research tool because it accurately replicates firebrand showers, matching the size, shape and mass of real firebrands. For example, by pointing the dragon at things like fences and shingles, scientists can better understand the vulnerabilities of those structures to ignition. The NIST Dragon is the basis for the international standard ISO 6021, allowing labs worldwide to collect and share consistent data on firebrand behavior.

To characterize the embers created by the NIST Dragon, NIST also created the “Emberometer,” a device that uses digital cameras to measure firebrands in flight.

Protection of Structures

Buildings are at risk from both fire and embers. NIST staff have measured how combustibles near a building — like landscaping, fences and sheds — can catch fire from flames and firebrands and then ignite the building.

Working with partners, NIST developed guidelines for protecting these combustibles, approaches to property maintenance, and building codes to make homes in wildfire-prone areas more fire-resistant.

For example, NIST discovered that firebrands can enter buildings through air vents and ignite materials inside. To study this hazard, they worked with Japan’s Building Research Institute, using the NIST Dragon to shower firebrands on a building inside a wind tunnel. Different vent grates were tested, and NIST staff found that firebrands stuck against the grating, where they burned down until they fit through holes even smaller than 1 millimeter (0.04 inch). NIST continues to work with partners to address these unregulated hazards.

Preventing Wildfires from Spreading: Insights from Cutting-Edge Fire Experiments — Real-life fire experiments are providing new insights into the complex question of how far apart two structures, such as a house and a shed, should be in order to limit the risk of fire spreading from one to the other. The experiments conducted by the National Institute of Standards and Technology, in collaboration with CAL FIRE, the U.S. Forest Service, and the Insurance Institute for Business and Home Safety examine how fires spread from sheds of different sizes and with a range of fuels to identify critical separation distances. This information will be used to develop better building codes and preventive measures to mitigate the impact of wildfires.

Community Protection

Fire behaves differently from other disasters. With something like an earthquake or a flood, the more intense the initial disaster is, the more damage it causes. But even a very small initial fire can lead to a lot of damage as it spreads from vegetation to structures.

Traditional fire codes only apply to individual buildings or parcels of land. But for preventing a WUI fire, it’s also important to look at the community as a whole to reduce the risk that a fire will spread.

To address this, NIST, the California Department of Forestry and Fire Protection (CAL FIRE), and the Insurance Institute for Business & Home Safety (IBHS) developed the Hazard Mitigation Methodology (HMM). This science-based approach is built on data from post-fire observations, field analysis and lab research. It considers factors like building separation and parcel layouts, showing how both community and structural fire protection are essential. CAL FIRE is using the HMM to retrofit six California communities, paving the way for future state and national codes.

The United States Fire Administration (USFA) and NIST are working to make HMM part of the national strategy to manage wildland fires. The International Code Council is also planning to include HMM principles in the 2027 edition of the International Wildland-Urban Interface Code.

Planning ahead for evacuation is another important way to reduce fire injury and death. In 2023, NIST issued ESCAPE, a system for communities to prepare for fire evacuations. ESCAPE is based on post-fire observations and focuses on evacuating small and intermediate-sized WUI communities, especially when there’s not enough time to evacuate fully. ESCAPE is the only national WUI evacuation guide and is already being used by 30 California communities.