Framework for Addressing the National Wildland Urban Interface Fire Problem--Determining Fire and Ember Exposure Zones Using a WUI Hazard Scale (NISTTN 1748)

Published: January 14, 2013


Alexander Maranghides, William Mell


WUI fires offer a unique challenge to the fire fighting and fire protection engineering communities. The scale of the events can be vast, spanning in many cases over 100,000 acres (40,000 ha) and the number of structures involved can range into the thousands. The severity of the fire intensity is dependent on vegetative (wildland and ornamental) and structural fuels, topography, and weather. Compared to hurricanes and earthquakes, fire intensity can vary significantly over relatively short distances (fractions of a mile) resulting in complex fire suppression and evaluation operations. A scale needs to be created to help quantify the severity of WUI events. Once established, a technically based ember and fire exposure scale or M-scale for the WUI can then form the technical foundation for a set of building codes aimed at providing a level of structure ignition protection commensurate with the expected exposure from fire and embers. The M-scale concept is based on quantifying fire and ember exposure throughout an existing WUI community. The proposed M-scale could then be used to determine exposure zones for new and existing WUI communities. Additionally, the exposure scale can be linked to first responder and homeowner safety.
Citation: Technical Note (NIST TN) - 1748
Report Number:
NIST Pub Series: Technical Note (NIST TN)
Pub Type: NIST Pubs


Wildland, Wildland Urban Interface, WUI, fire exposure, ember exposure, M-scale
Created January 14, 2013, Updated November 10, 2018