Author(s): Kathleen Almand. Published on September 3, 2014.

AS THE 2014 WILDLAND FIRE SEASON RAGES, I am reminded of the reason that NFPA has identified fire safety at the wildland/urban interface (WUI) as a priority for its current strategic plan. 

NFPA’s Fire Analysis and Research Division reports that nine of the 25 costliest fires in U.S. history, in terms of property loss, are described as forest, wildland, or wildland/urban interface fires. This isn’t just a U.S. problem; the International Association of Wildfire reports that structures lost to fires in the WUI have grown significantly over the past 20 years. This trend is the result of many factors, including increased development in rural areas, fuel management policies, and climate change, all of which are projected to continue for the forseeable future.

As part of our renewed focus on this topic, NFPA has recently restructured the technical committees responsible for
NFPA 1144, Reducing Structure Ignition Hazards from Wildland Fire, and NFPA 1141, Fire Protection Infrastructure for Land Development in Wildland, Rural, and Suburban Areas, the standards that address hazards to structures in the wildland/urban interface as well as the appropriate mitigation measures. The Fire Protection Research Foundation has been tasked with assembling the most recent information on the fire risk at the WUI to help inform the activities of these committees. One such project, “Pathways for Building Fire Spread in the Wildland/Urban Interface,” will generate a report later this fall.

When we think of wildland fire risks for communities, our inclination is to imagine what we’ve seen in the movies: a wall of fire descending on structures. In fact, there are three fundamental pathways for wildland fires to spread into and within WUI communities. Direct flame contact and local radiation—the movie model—may occur when the fire front is nearby, and we have focused a lot of our attention and resources over the years on this pathway to ignition. The concept of maintaining a clear defensible space around the home was developed to address this form of fire spread and serves as the basis for a lot of protection guidance, including
NFPA’s Firewise® program.

A second common method of fire spread into and within WUI communities is through wind-driven transport of firebrands, or embers, capable of igniting combustible exterior surfaces. Recent data from investigations by the National Institute of Standards and Technology (NIST) on recent large-loss WUI fires show that up to 50 percent of ignitions are due to this form of indirect exposure, and that roofs, decks and other exterior elements remain vulnerable to this form of fire spread. Finally, while we have traditionally thought of the burning wildland itself as the source of ignition, nearby structures that have been ignited can also present a threat to adjacent properties, either through radiation exposure or transported embers. This means of fire spread within WUI communities can threaten homes located some distance from wildland areas.

NFPA isn’t the only organization with an increased research focus on the wildland/urban interface. A variety of organizations, including NIST, the U.S. Forest Service, and the Insurance Institute for Business & Home Safety, to name a few, are actively pursuing research programs to better understand the spread of fire from the wildland to structures. The Foundation’s goal is to serve as a bridge between this emerging research and NFPA’s codes and standards so that our prevention and protection strategies reflect our new and growing understanding of WUI firespread.