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Reduced Ignition of Building Components in Wildland-Urban Interface (WUI) Fires Project


Over 46 million homes in 70,000 communities are at risk of Wildland-Urban Interface fires, which has destroyed an average of 3000 structures annually over the last decade and is rapidly growing1, 2. Within the last 100 years in the U.S., six of the top 10 most damaging single fire events involving structures were WUI fires. The WUI fire problem is a structure ignition problem. To reduce the risk of structural ignition, the technical basis for improved test standards and building codes are being developed. Post-fire damage assessment evidence suggests that firebrands (embers) are a major source of structural ignition in WUI fires. A unique experimental apparatus, known as the NIST Firebrand Generator (NIST Dragon), has been constructed to produce a controlled and repeatable firebrand attack. The experimental results generated from the marriage of the NIST Dragon to the Building Research Institute’s (BRI) Fire Research Wind Tunnel Facility (FRWTF) in Japan are being used by standards organizations to guide the development of new standards and provide the scientific basis for new performance-based requirements with the intent to make structures more resistant to firebrand attack. The results of this research will allow improved fire-resistance of building components, structures and communities which will resilience of WUI communities.


Objective: To reduce the risk of structural ignition during a WUI fire by developing, by 2016, the technical basis for new and improved standard laboratory test methods and building codes.

What is the new technical idea? The new technical ideas are to use full scale experiments and computer modeling to quantify the vulnerability of structures to ignition in WUI fires. The full scale experiments will use a unique experimental apparatus, the NIST Firebrand Generator (or NIST Dragon). The NIST Dragon can generate a controlled firebrand shower on a realistic scale and direct this firebrand shower onto components of a structure to ascertain their resistance to ignition as a part of a full scale structural system. The full scale experiments will be targeted to specific vulnerabilities observed from NIST’s post-fire field studies of structures exposed to actual WUI fires. Finally, experimental results obtained from this work will be used to generate a database to validate NIST’s WUI Fire Dynamics Simulator (WFDS) for brand transport and structural ignition. WFDS will be used to guide/assess standard laboratory test methods and building codes by allowing exposure conditions to be simulated over a broad parameter space.

What is the research plan? With the development of the NIST Dragon technology, it has been possible, for the first time, to quantify vulnerabilities of structures to wind-driven firebrand showers. When WUI fires spread into communities, the combined influence of firebrand showers, and radiative heat flux, is believed to contribute to ignition of structures. Radiative heat flux is generated as vegetation and other structures burn in WUI fires within communities. Due to no known measurement science in this area, it has not been possible to investigate the importance of such coupled ignition mechanisms. In FY14, an experimental apparatus will be constructed. The recently developed NIST Full Scale Continuous Feed Dragon will be combined with a modified Intermediate Scale Calorimeter (ICAL) to investigate the combined influences of wind-driven firebrand showers in the presence of radiative heat flux.

The ICAL is described in ASTM E16233 and has been designed to provide a uniform and well controlled radiative flux onto building elements. For the purposes of the work in FY14, the ICAL will be re-designed into two separate vertical radiant panels. These panels will be positioned onto the sides of the NIST Dragon. This new apparatus will be constructed at NIST, and will be used to investigate building component exposure under combined wind-driven firebrand showers in the presence of radiative heat flux. Once coupled with a well characterized wind field, typically in a wind tunnel, this new apparatus will enable experimentation over a broad range of exposure conditions. Assemblies that have been indentified to be vulnerable in WUI fires based on post-fire surveys (e.g. fences, decks) will be experimented with using this new apparatus. This new measurement science capability directly feeds into the recently EL-NIST developed WUI Hazard Scale, since it will be possible to expose any type of building assembly to different levels of combined fireband and radiative flux, thus enabling the ability to design structures to various exposures.


[1] U.S. Communities Dealing with WUI Fire Fact Sheet (ICC) 1.1.2011; Headwaters Economics,

[2] WUI Fact Sheet, Communities Dealing with Wildland/Urban Interface Fire, International Code Council;, and Natural Association of Resource Conservation & Development Councils.

[3] ASTM E1623-11 Standard Test Method for Determination of Fire and Thermal Parameters of Materials, Products, and Systems Using an Intermediate Scale Calorimeter (ICAL), ASTM International, West Conshohocken, PA, 2011.

Major Accomplishments:

Research Outcomes:

  • Firebrands Generated from a Full-Scale Structure Burning Under Well-Controlled Laboratory Conditions, Fire Safety Journal, in review, Suzuki, S., Brown, A., Manzello, S.L., Suzuki, J., and Hayashi, Y.;
  • Summary of Workshop for Fire-Structure Interaction and Urban and Wildland-Urban Interface (WUI) Fires – Operation Tomodachi Fire Research, Fire Safety Journal, accepted press, 2013, Manzello, S.L., Yamada, T., Jeffers, A., Ohmiya, Y., Himoto, K., and Fernandez-Pello, A.C.;

Potential Research Impacts:

  • Wildland-Urban Interface (WUI) Fires, Manzello, S.L. (Editor), Special Issue of Fire Technology, published on-line, FY2013.
  • Characterizing Firebrand Exposure from Wildland-Urban Interface (WUI) Fires: Results from the 2007 Angora Fire, S.L. Manzello and E.I.D. Foote, Fire Technology, published on-line, FY2013.
  • The Size and Mass Distribution of Firebrands Collected from Ignited Building Components Exposed to Wind, S. Suzuki, S.L. Manzello, and Y. Hayashi, Proc. Combust. Inst., 34: 2479-2485, FY2013.
  • Large Outdoor Fires Special Issue, Manzello. S.L., and Himoto, K. (Editors), Fire Safety Journal, 54: 143, (FY2013);
  • Enabling the Study of Structure Vulnerabilities to Ignition from Wind Driven Firebrand Showers: A Summary of Experimental Results, S.L. Manzello, S. Suzuki, and Y. Hayashi, Fire Safety Journal, 54:181-196 (FY2013);
  • Firebrand Generation Data Obtained from a Full Scale Structure Burn, S. Suzuki, S.L. Manzello, M. Lage, and G. Laing, Int’l J. Wildland Fire, 21:961-968 (FY2012);
  • The New and Improved Dragon’s LAIR (Lofting and Ignition Research) Facility: Coupling the Reduced Scale Continuous Feed Firebrand Generator to Bench Scale Wind Tunnel, S.L. Manzello and S. Suzuki, Fire and Materials Journal, 36:623-635 (FY2012);
  • Exposing Siding Treatments, Walls Fitted with Eaves, and Glazing Assemblies to Firebrand Showers, S.L. Manzello, S. Suzuki, and Y. Hayashi, Fire Safety Journal, 50: 25-34, (FY2012);

Realized Research Impacts:

  • Firebrand Generation from Burning Vegetation, Manzello, S.L., Maranghides, A., and Mell, W.E., International Journal of Wildland Fire, 2007,16, 458-462; (FY2007)  
    Characterized vegetation embers that result in over 50% of WUI ignitions.
  • Experimental Investigation of Fire Brands: Generation and Ignition of Fuel Beds, Manzello, S.L., Cleary, T.G., Shields, J. R., Maranghides, A., Mell, W.E., and Yang, J.C., Fire Safety Journal, 2008, 43,226-233; (FY2008)
    Demonstrated the role that firebrands play in WUI ignitions.
  • On the Development and Characterization of a Firebrand Generator, Manzello, S.L., Shields, J. R., Cleary, T.G., Maranghides, A., Mell, W.E., Yang, J.C., Hayashi, Y., and Kurita, T., Fire Safety Journal, 2008 43, 4, 258-268; (FY2008)
    Provides technical basis to develop first apparatus to generate standard set of firebrands for testing response of building components and structures to firebrand exposure.

Impact of Standards and Tools:

  • Continuous Feed Standard Firebrand Generator. (FY2011)
  • Standard Firebrand Generator Apparatus replicated by Insurance Institute for Business and Home Safety, Underwriter’s Laboratory, and University of Coimbra, Portugal, for standardized testing of roofing, siding, and glazing materials. (FY2011-FY2013)
  • Standards that are currently being balloted, but not yet adopted include ASTM E05.14 Fire Brand Resistant Building Vents. The NFPA and ASTM standards are used nationally, while the California Code of Regulations is a model often adopted by others states.
  • Regulations that have incorporated NIST procedures include the California Code of Regulations – Chapter 7A WUI Building Standards (2009 Supplement to 2007 Edition), FY2009.
NIST's Firebrand Generator generates burning embers (or firebrands) that are major sources of ignition of house fires during blazes at the wildland-urban interface (WUI). Photo credit: NIST
NIST's Firebrand Generator generates burning embers (or firebrands) that are major sources of ignition of house fires during blazes at the wildland-urban interface (WUI). Photo credit: NIST

Start Date:

October 1, 2011

Lead Organizational Unit:


Facilities/Tools Used:



General Information:
Dr. Samuel L. Manzello, Project Leader
301-975-6891 Telephone

100 Bureau Drive, M/S 8662
Gaithersburg, MD 20899-8662