Journal Article Examines the Combustion Behavior of Pressure Treated Wood and Wood-Plastic Composite Exposed to Firebrands

A new peer-reviewed journal article, Ignition and Combustion Behavior of Pressure Treated Wood and Wood-Plastic Composite Exposed to Glowing Firebrand Piles: Impact of Air Flow Velocity, Firebrand Coverage Density and Pile Orientation, has been published in the Fire Safety Journal. The article was co-authored by collaborators from University of Maryland (UMD), University of Melbourne (UoM), University of California, Berkeley, and the Fire Safety Research Institute (FSRI), part of UL Research Institutes. The research and analysis performed in the study was led by Alec Lauterbach, a graduate student in Dr. Stanislav Stoliarov’s research group at UMD and is part of the Firebrand Ignition of Building Materials research project.

The Impact of Firebrand Exposure to Building Materials

There is a growing risk of wildfires worldwide, especially in wildland urban interface (WUI) communities. There are a variety of causes for WUI fire spread including direct flame impingement, radiant heat exposure, and firebrand exposure. 

This article examines pressure treated wood (PTW) and wood-plastic composite (branded as Trex®) when exposed to glowing firebrand piles in a bench-scale wind tunnel. Researchers collected data on heat release rate and combustion efficiency during a series of experiments that resulted in several types of flaming ignition events. Several observations were made during experimentation and analysis:

• Ignition frequency increased with increasing air flow and firebrand coverage density within the range of the tested parameters.
• Wood-plastic composite was less prone to preleading zone ignition but more prone to igniting downstream of the pile.
• Pressure treated wood was more likely to sustain smoldering.

“Exposure to firebrand showers frequently leads to loss of structures in large wildland-urban interface fire events. To mitigate the impact of wildland-urban interface fires, it is important to understand the mechanism by which firebrands ignite building materials. This study lays the foundation for the development of this understanding.”
—Stas Stoliarov, professor, University of Maryland

Read the peer reviewed journal article

This work was funded through the International Fire Safety Consortium (IFSC) partnership.

Abstract

Pressure treated wood (PTW) and wood-plastic composite (Trex®) were exposed to glowing firebrand piles in a bench-scale wind tunnel. The air flow velocity was 0.9–2.7 m s-1, the firebrand coverage densities were 0.06 and 0.16 g cm-2, and the pile footprint was 5×10 cm2 with either the 10-cm or 5-cm sides perpendicular to the incident air flow. Several types of flaming ignition events were observed including flames attached to the substrate surface in front of the pile (preleading zone ignition), and flames attached to the pile that sometimes spread onto the substrate downstream of the pile (downstream ignition). The most frequent and long-lasting flaming combustion occurred in experiments performed at 2.4–2.7 m s-1 using 0.16 g cm-2 firebrand coverage density piles with 10-cm sides perpendicular to the air flow. Trex® was less prone to pre-leading zone ignition but was more prone to downstream ignition. Unlike Trex®, PTW exhibited a propensity for sustained smoldering for a wide range of air flows.

About the Fire Safety Journal:

The Fire Safety Journal is the leading publication dealing with all aspects of fire safety engineering. Its scope is purposefully wide, as it is deemed important to encourage papers from all sources within this multidisciplinary subject, thus providing a forum for its further development as a distinct engineering discipline. This is an essential step towards gaining a status equal to that enjoyed by the other engineering disciplines.