Letter from the Editor: Welcome to the September 2009 issue of Fire Protection Engineering Emerging Trends, Fire Protection Engineering magazine's 8-time-per-year e-newsletter that deploys on the off-months of the magazine. Each issue will highlight a new trend and/or innovation in the fire protection engineering industry. This issue will focus on the challenges and pitfalls of defining exposure at the wildland urban interface.

Please enjoy the September issue and thank you for your continued support!

Sincerely,

Morgan J. Hurley, P.E.

By Alexander Maranghides

Even amongst fire protection engineers, the term "exposure" can mean different things. When investigating human tenability, "exposure" typically refers to toxic gases, heat fluxes and temperature. When conducting a design calculation on the response of a structural member to a specific design fire, "exposure" typically refers to the heat fluxes and temperatures that will impact a structural element during a design fire. In both cases, in order to correctly characterize exposure, one must clearly define the fire scenario as well as the progression of the fire event. Complications arise when the selected design fire does not adequately represent the real life fire scenario. This typically occurs because either the fire scenario is not clearly understood or from an inappropriate determination of equivalent fire exposure.

The Wildland Urban Interface (WUI) has many definitions; however, for the purposes of this article, WUI refers to locations where topographical features, vegetation types, local weather conditions and prevailing winds result in potential for ignition of structures from flames and embers of a wildland fire.¹

Between October 2003 and October 2007, seven California WUI fires destroyed a total of 8,877 structures² - on average over 2,200 structures per year. These seven fires resulted in 29 deaths, and over 317,000 hectares (783,000 acres) burned. The 2003 Cedar fire and the 2007 California Firestorm are among the top four fire incidents for the number of structures destroyed and acres burned. The Witch fire, the largest of the fires that occurred during the 2007 California firestorm, burned 80,124 hectares (197,990 acres) and destroyed 1,125 residential structures, 509 outbuildings and 239 vehicles. Additionally, 77 residential structures and 25 outbuildings were damaged.³

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Traditionally, passive and active fire protection measures in structures have been aimed at limiting the spread and damage from a fire initiating inside the home. A paradigm shift is needed for structures that resist ignitions from both the inside and outside. However, very little quantitative information is available on the actual exposure experienced by structures in WUI fire settings.

Even though there are other fuel sources, structures at the WUI typically ignite from other structures or from residential or wildland vegetation. Traditionally, it had been believed that the ignition process was driven by direct flame contact or radiative heating. Embers have been known to play a role in the ignition process during WUI fires.^3,4

To predict the ignition of structures from WUI fires, the production of embers from different types of vegetation and from burning structures needs to be characterized. However, removing embers as a source of structure ignition will not solve the problem of structure to structure fire spread in its entirety.

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The Annual Meeting: SFPE Professional Development Conference and Exposition: October 17-23, 2009

Plan on attending this year's SFPE Annual Meeting at the Doubletree Paradise Valley Resort in Scottsdale, Arizona. It will provide you an opportunity to learn new developments in fire protection engineering. A two-day Engineering Technology Conference will be held that highlights advanced and cutting-edge practices in fire protection engineering that are used to protect people, property and the environment from fire.

The conference creates a unique educational experience that is designed to keep you a step ahead of the rest. The Engineering Technology Exposition and a series of seminars taught by the profession's leaders will follow the two-day technology conference. Seminars scheduled are:

• New! Beyond Cause and Origin: Engineering Analysis of Building Fires

• Revised! Sprinkler Design for the Engineer - Updated to the 2010 Codes

• Revised! Advanced Fire Alarm Systems Design - Updated to the 2010 Codes

• Dust Explosion: Hazard Recognition, Assessment and Management

• Principles and Application of Egress Modeling

• Principles of Fire Protection Engineering

• Advanced Fire Dynamics Simulator and Smokeview

• Smoke Control Session I: Fundamentals and Pressurization Systems

• Smoke Control Session II: Design Fires, Atrium Control and Tenability Systems

• Smoke Control Session III: CONTAM Analysis of Pressurization Systems

Click here for the most up-to-date information and to register.

SFPE Engineering Technology Exposition will open on Tuesday, October 20, 2009

Exhibit space and sponsorship offers a unique opportunity to promote your products and services that will position your company as a leader in the fire protection engineering community. For more information on being an exhibitor or sponsor, click here or contact Elle Andracsek at (301) 915-9721 or eandracsek@sfpe.org.

The experiments showed that an adjacent structure can be ignited if flames from a fire inside a house exit through window openings. The experiments illustrated how a fire resistant barrier can, in the scenario tested, slow down flame spread between two structures separated by 1.8 m (6 ft). The scenarios tested were not the worst case. Flame spread between structures is a complex process primarily affected by structure construction type, structure separation distance, placement and size of windows and weather conditions. The experiments illustrated the impacts of high density single family construction on fire spread.

This limited data on the actual contribution of embers to structure ignitions has limited the development of ember specific test methods for building materials and systems. As an example, the Standard for Tests for Fire Resistance of Roof Covering Materials⁶ is designed to evaluate a roof assembly's ability to resist fire exposure from the outside. The maximum wind used in the test is only set to 19 km/h (12 mph), less than the severe weather conditions seen during many WUI fires. Additionally, the test is not designed to challenge the roof assembly against dynamic ember assault present during severe WUI fires. As new data on the significance and impact of embers become available, the testing community is quickly responding. Recently, the ASTM International Committee E05 formed subcommittee E05.14 specifically for External Fire Exposure Tests.

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Engineers have tools available for addressing parts of the problem. Fire dynamics provides the foundation, while computer models such as the Fire Dynamics Simulator (FDS)⁷ and other models offer methods to simulate fire behavior. The tools, however, will only work as well as the engineer can correctly understand the evolution of the fire scenario. Understanding the exposure ultimately requires understanding the fire environment.

Alexander Maranghides is with the National Institute of Standards and Technology.

1. NFPA 1144, Standard for Reducing Structure Ignition Hazards from Wildland Fire, National Fire Protection Association, Quincy, MA, 2008.
2. Anon, "The 20 Largest California Wildland Fires (By Structures Destroyed)," CALFIRE Communication, January 12, 2009. Available from http://www.fire.ca.gov/communications/downloads/fact_sheets/20LSTRUCTURES.pdf.
3. Maranghides, A. and Mell, W., "A Case Study of a Community Affected by the Witch and Guejito Fires," NIST Technical Note 1635, National Institute of Standards and Technology, Gaithersburg, MD, 2009.
4. Leonard, J. and Blanchi, R., "Investigation of Bushfire Attack Mechanisms Resulting in House Loss in the ACT Bushfire 2003," A CRC Bushfire Report, Bushfire CRC Report CMIT Technical Report - 2005-478, Bushfire Cooperative Research Centre, East Melbourne, Australia, 2005.
5. Maranghides, A. and Johnson, E., "Residential Structure Separation Experiments," NIST Technical Note 1600, National Institute of Standards and Technology, Gaithersburg, MD, 2008.
6. ASTM E108, "Standard Test Methods for Fire Tests of Roof Coverings," ASTM International, West Conshohocken, PA, 2007.
7. McGrattan, K., et al., "Fire Dynamics Simulator (version 5) User's Guide," NIST Special Publication 1019-5, National Institute of Standards and Technology, Gaithersburg, MD, 2009.

FPE Winter 2005 – Challenges Facing Engineered Structural Fire Safety – A Code Official's Perspective
The question has been raised whether prescriptive building codes provide adequate protection for structures. The economic losses along with the attendant costs to society in the three cases looked at in this article would argue equally that the prescriptive building code requirements are lacking. The organizations that promulgate building codes are trying to write codes that are more "performance-based" and less prescriptive, to increase design flexibility. Increasingly, analyses and reports from fire protection engineers are being provided to code officials in lieu of traditional fire protection of structures. In the atmosphere of increasing demand for fire protection engineering and the increasing sophistication of the analytical tools available to the fire protection engineer, it must be recognized that code officials will ultimately decide what will be permitted for protection of structures. There are many challenges facing the code official (and by extension, the fire protection engineer) before engineered fire protection can become widely accepted.
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FPE Summer 2003 – The Development of Cesare Risk
The value of an holistic approach to fire safety in buildings has long been recognized in Australia. This may be because even urban dwellers in Australia are well aware of the potential for destruction and the threat from unwanted fires. However, it is comparatively recently that building code writers and enforcers have become aware, supportive, and accepting of risk oriented approaches to fire safety. These efforts have resulted, among other things, in the development of CESARE Risk (a building fire-risk cost-assessment computer model also sometimes known as Fire Risk) substantially through the financial support of Australian building code authorities along with the adoption by the Australian Building Codes Board (ABCB) and the state Authorities Having Jurisdiction of a performance-and risk-oriented approach to building regulation development and reform.
READ MORE

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SFPE Job Board

http://jobs.sfpe.org/

The Society of Fire Protection Engineers and Fire Protection Engineering magazine are pleased to offer an Internet Job Board site featuring career opportunities in fire protection engineering.

http://jobs.sfpe.org/ is designed for communicating the availability of employment opportunities in the fire protection engineering market. This special job board is ideal both for those seeking to fill positions and those looking for employment opportunities in
fire protection engineering.

Job categories include:
• Consulting
• Research & Testing
• Government
• Fire Equipment Manufacturing & Installation
• Insurance
• Education

Whether you're looking to make a career move, or you need to fill a fire protection engineer opening, http://jobs.sfpe.org/ is just a click away!

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Join the Society of Fire Protection Engineers

The Society of Fire Protection Engineers (SFPE) is the professional organization that represents fire protection engineers worldwide. Through its membership of over 5,000 professionals and 60 chapters, SFPE advances the science and practice of fire protection engineering internationally. For more information, visit http://www.sfpe.org/Membership.aspx.

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