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Parcel Combustibles

This photo shows the test setup from a point of view behind and to the right of the fan. The fan and flow straightener are in the foreground, and beyond can be seen a smoking mulch bed, the shed, and some instrumentation, including a camera and the bidirectional probe array that measures wind.
Photo of test site showing fan, flow straightener and target shed in an experiment on a mulch bed without a fence.
Credit: Rik Johnsson/NIST

Field observations show that combustible landscaping features are a common pathway leading fire spread directly to homes during wildland-urban interface (WUI) fires. NIST is studying how these features around a home burn to better understand their levels of hazard and potential roles in spreading WUI fires. Three series of field experiments, focused on fences and mulch, firewood piles, and landscape timbers, were conducted to examine how fire spread toward a structure (a small shed) under conditions that may be encountered during a WUI fire. The results of these studies are intended to better inform standards and codes regarding placement of landscape features around homes that are at risk of exposure to wildland-urban interface fires.

In these experiments, an airboat-style wind machine was used to generate a wind field at three speeds to determine wind’s effect on fire spread via flames and firebrands. For most experiments, a target mulch bed at the base of the structure evaluated the ability of firebrands produced by the burning objects to ignite spot fires that could threaten the structure.

A photo of two back-to-back wood privacy fence panels spaced eight inches apart burning in front of a shed. The flames engulf the entire set of fences and extend more than three feet above them.
A photo of two back-to-back wood privacy fence panels spaced eight inches apart burning 1.8 m (6 ft) from a shed under 6 m/s (13 mi/h) winds.
Credit: Rik Johnsson/NIST


PUBLICATIONS

Butler, K. and Johnsson, E., et al. (2022) Wind-Driven Fire Spread to a Structure from Fences and Mulch. NIST Technical Note 2228.
https://doi.org/10.6028/NIST.TN.2228-upd1

Johnsson, E., et al. (2023) Wind-Driven Fire Spread to a Structure from Firewood Piles. NIST Technical Note 2251.
https://doi.org/10.6028/NIST.TN.2251

Butler, K., et al. (2023) Wind-Driven Fire Spread to a Structure from Composite Fences. NIST Technical Note 2357.
https://doi.org/10.6028/NIST.TN.2357

Johnsson, E., et al. (2025) Wind-Driven Fire Spread to a Structure from Landscape Timbers NIST Technical Note 2307.
https://doi.org/10.6028/NIST.TN.2307

Fire and Wildland urban interface fire

Contacts

Created September 29, 2026, Updated September 30, 2026
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