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Effects of Wind Speed and Angle on Fire Spread along Privacy Fences

Published

Author(s)

Erik L. Johnsson, Alexander Maranghides

Abstract

A series of experiments was conducted to examine fire spread along fences subjected to wind at various speeds and angles. Specifically, sections of western redcedar, California redwood, or vinyl privacy fences were ignited with a burner. Wind fields of 9 m/s, 13.5 m/s, or 18 m/s aligned with, perpendicular to, or at a 45° angle to the fences were applied during the experiments. To simulate fine fuels typically present in real installations, dried shredded hardwood mulch beds were placed under most of the fence sections. Also, some fence sections were coated with fence preservative to assess its effect on fire spread. Pans of mulch were downwind targets for embers produced by the burning fence and mulch bed. At all wind speeds tested, a mulch bed was required for flames to spread. Fastest flame spread was achieved with the fence aligned with the wind field. During most experiments, the burning mulch and fences produced embers which ignited spot fires in the mulch targets. These experiments demonstrated that ignited wood fence structures can be rapid conduits for fire along them and potentially spread fire to attached or adjacent structures. Additionally, it was found that burning fences can produce spot fires from their own ember generation. This study of fence fire spread is part of a series designed to better inform standards and codes regarding placement of landscape features around homes at risk of exposure to wildland-urban interface fires.
Citation
Technical Note (NIST TN) - 1894
Report Number
1894

Keywords

WUI fires, firebrands, embers, wildland urban interface fires, fence fires, structural ignition, structural embers, fire spread
Created July 25, 2016, Updated November 10, 2018