Flame Spread Along Fences Near a Structure in a Wind Field

Published

October 20, 2017

Author(s)

Kathryn M. Butler, Erik L. Johnsson, Marco G. Fernandez, Mariusz Zarzecki, Eric Auth

Abstract

Combustible fences have been identified in post-fire investigations of wildland-urban interface (WUI) fires as potential threats to homes and other structures. They may ignite due to direct fire contact or firebrands, they may conduct fire along their length, and they may become sources of firebrands themselves. The fire threat to structures posed by nearby fences in a WUI fire was studied in a series of field experiments. Flame spread rates and firebrand ignition characteristics were obtained for a fence in front of a structure in a wind field. A western redcedar fence assembly was placed perpendicular to the wall of a small structure, separated from the structure by distances of 0 m, 0.30 m, 0.91 m, or 1.83 m. A wind field of 11 m/s aligned along the fence was generated by a large fan modulated by a flow straightener. The rate of flame spread for the fire moving continuously along the base of the fence was found to be a strong function of separation distance, with spread rates nearly an order of magnitude faster for 1.83 m separation distance than for either 0 m or 0.30 m. For each separation distance, a time delay was observed before firebrands began to ignite spot fires in the mulch bed next to the structure. After the first spot fire was observed, several others followed quickly. In every case except one, spot fires carried the fire to the structure wall within 7 min. In the exceptional case, little spotting was observed, and the fire took over 20 min to reach the wall.

Proceedings Title

Fire Safety 2017 - International Conference on Research and Advanced Technology in Fire Safety

Conference Dates

October 20-21, 2017

Conference Location

Santander

Pub Type

Conferences

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Keywords

flame spread, wildland-urban interface fires, structural response, firebrands.

Citation

Butler, K. , Johnsson, E. , Fernandez, M. , Zarzecki, M. and Auth, E. (2017), Flame Spread Along Fences Near a Structure in a Wind Field, Fire Safety 2017 - International Conference on Research and Advanced Technology in Fire Safety, Santander, -1, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=922111 (Accessed May 10, 2024)