Urban-Wildland Fires: On the Ignition of Fuel Beds by Firebrands. (POSTER ABSTRACTS)
Urban-Wildland Fires: On the Ignition of Fuel Beds by
Firebrands. (POSTER ABSTRACTS)
(101 K)
Manzello, S. L.; Cleary, T. G.; Shields, J. R.; Yang, J.
C.
POSTER ABSTRACTS;
Fire Safety Science. Proceedings. Eighth (8th)
International Symposium. (POSTER ABSTRACTS).
International Association for Fire Safety Science
(IAFSS). September 18-23, 2005, Beijing, China, Intl.
Assoc. for Fire Safety Science, Boston, MA, Gottuk, D.
T.; Lattimer, B. Y., Editor(s), 1637-1637 p., 2005.
Keywords:
fire research; fire safety; fire science; urban/wildland
interface; ignition; fuel beds; fire brands;
computational fluid dynamics
Abstract:
Urban-wildland fires have plagued the United States for
centuries. Recent urban-wildland fires include the 2002
Hayman Fire, the 2000 Los Alamos Fire, and the 1991
Oakland Hills Fire. Fires in the urban wildland
interface can have a devastating effect on human life,
property loss, and local economies. Embers or firebrands
are produced as trees and other objects burn in
urban-wildland fires. These firebrands are entrained in
the atmosphere and may be carried by winds over long
distances. Hot firebrands ultimately come to rest and
may ignite fuels far removed from the fire, resulting in
fire spread. This process is commonly referred to as
spotting. Understanding how these hot firebrands can
ignite surrounding fuels is an important consideration
in mitigating fire spread in communities. A major
advance in urban-wildland fire research would be the
development of a model to predict the ignitability of
materials due to firebrand impact. The lack of a
detailed theory on the ability of firebrands to ignite
remote objects limits the utility of detailed
computational fluid dynamic models (CFD) that could be
used to predict fire spread by firebrands. Detailed
experimental ignition studies of fuel beds typically
found in the urban-wildland interface due to firebrand
impact are required to validate such models.
Consequently, an experimental apparatus has been built
to investigate the ignition of fuel beds as a result of
impact with burning firebrands. The apparatus allowed
for the ignition and deposition of firebrands onto the
target fuel bed. The moisture content of the fuel beds
used was varied and the fuels considered were pine
needle beds and shredded paper beds. Pine needle beds
were intended to simulate gutters filled with pine
needles. Shredded paper beds were used as a surrogate
for typical cellulosic fuels that would be found in
attic spaces. Firebrands were simulated by machining
wood (pinus ponderosa) into small disks of uniform
geometry. The firebrand ignition apparatus was installed
into the Fire Emulator/Detector Evaluator (FE/DE) to
investigate the influence of an air flow on the ignition
propensity of fuel beds. Results of this study are
presented.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899