Fighting Fires With Science

Learning how to ‘dragon-proof’ buildings

Published: Thursday, July 7, 2016 - 15:07

I’m a dragon wrangler. Although that might sound like something straight out of Harry Potter or Game of Thrones, this isn’t fantasy—it’s serious science.

As a fire researcher, or more colloquially, a dragon wrangler, my job is to help protect people and property from fire’s devastating effects. My area of expertise is wildfires, and in particular wildfires that threaten whole communities, which we call wildland-urban interface (WUI) fires. In the United States alone there are more than 80,000 wildfires every year. A little more than 2 percent of those fires threaten populated areas, putting 46 million structures and more than 120 million people at risk. Every year, we lose about 3,000 homes to these kinds of fires.

The “Beast” wildfire that swept through Fort McMurray, Alberta, Canada, displaced 88,000 people for a month; destroyed about 2,400 homes, businesses, and other buildings; and shut down almost a quarter of Canada’s oil production. For me, watching the news reports and seeing the violence with which that wildfire swept through the town underscored the need for more WUI fire research. The loss of forest is unfortunate (although it’s a part of the natural cycle), but the loss of homes and lives is tragic and unnecessary.

WUI fires are a significant problem throughout the world. In the past few years, wildfires have affected Australia, Brazil, Chile, France, Greece, Portugal, Spain, and the United States. As the Fort McMurray fire graphically illustrated, it seems as though these fires are only getting worse.

In fact, President Obama was concerned enough that he recently signed an executive order to look into the potential effect that WUI fires could have on federal buildings.

Part of the reason that WUI fires give us so much trouble is that we don’t know much about them. Historically, most fire researchers have studied fires inside buildings. However, unlike a fire confined to a house, WUI fires are unconfined and exhibit incredibly complex behaviors driven by wind, weather, the kind of vegetation, and other factors. When vegetation and structures burn in WUI fires, pieces of burning material known as firebrands (embers) are carried off by the wind and start new fires. Showers of firebrands rained down on neighborhoods during the Fort McMurray fires and are a common characteristic of WUI fires worldwide.

Although the dangers of firebrand showers have been known for decades, little research has been done on them because they’re difficult to realistically replicate and measure. To do this, my colleagues and I at the National Institute of Standards and Technology (NIST) had to invent an entirely new experimental approach—the NIST Firebrand Generator. We just call it the Dragon.

You can learn more about our Dragon technology by watching the video below:

We use the Dragon to generate controlled, repeatable firebrand showers that act just like those from real WUI fires, a feat for which fire chief Ethan Foote and I won an annual award from the National Fire Protection Association.

Without standard laboratory test methods, fire researchers can’t evaluate or compare how well different building materials and architectural features like roofs and walls resist being ignited by firebrands. Our current understanding of how well these different building components stand up to WUI fires is still mainly based on informal reports made by untrained observers. As a result, the limited number of WUI building codes and standards we have lack scientific rigor and do not explicitly address firebrand exposure.

To develop firebrand-specific test standards, we need to design full-scale experiments that evaluate—piece by piece and feature by feature—a structure’s vulnerabilities to firebrand showers. For example, in WUI fires, firebrands may penetrate building vents, ignite wood decks and fences adjacent to structures, and blow under tile roofs. Any of these situations could set the building on fire.

Image 1: Typical of what you might find in your or your neighbor’s backyard, we set up an outside corner section of cedar fencing with a bed of shredded hardwood mulch next to it in the foreground. We exposed the cedar fencing to wind-driven firebrand showers moving at 8 m/sec from the mouth of the NIST Dragon. The firebrands first produced smoldering fires in the shredded mulch bed before beginning to flame a few minutes later (Photo credit: NIST).

It is critical for us to understand the performance of various full-scale building components when exposed to firebrand showers so that we can zero in on these and other structural weak points. In turn, this will help us determine how big we need to make building component sections to perform realistic standard laboratory tests.

Because firebrand showers are blown by the wind, and wind plays a major role in whether a structure ignites, our experiments also have to take wind into account. To do that, my colleagues and I, in partnership with the Building Research Institute and the National Research Institute of Fire and Disaster, set up our first international duty station in Japan. The Building Research Institute maintains the Fire Research Wind Tunnel Facility, one of the only full-scale wind tunnel facilities in the world designed specifically for fire experimentation. The National Research Institute of Fire and Disaster has a smaller-scale wind facility that houses a smaller version of the NIST Dragon, which we call the Baby Dragon.

The marriage of NIST’s Dragon technology and these experimental facilities is helping us gain new insights into how wind-driven firebrands interact with individual building components and whole structures.

Image 2: We exposed this section of a full-scale concrete tile roofing assembly to firebrand showers moving at 6 m/sec. We determined the size of the roofing assembly to use by observing full-scale roofing assembly performance exposed to firebrand showers using the NIST Dragon at the Building Research Institute. Our experiments showed that firebrands are able to slip under the roof tiles. (Photo credit: NIST)

It’s great to see that other research laboratories worldwide are reproducing our Dragon technology. For example, the Insurance Institute for Business and Home Safety has used the NIST Dragon design to generate firebrand showers in its new wind tunnel facility, which is ideal for large-scale demonstrations. Europe’s largest wildland fire institute, ADAI, with the University of Coimbra in Portugal, has developed the Portuguese Baby Dragon, which they based on our original design.

So, although the dragons I work with might not be exactly like the ones you find in Harry Potter or Game of Thrones, I still think they’re pretty cool. In particular, I’m looking forward to what they’re going to teach us about how to build more fire-resilient—you might even say “dragon-proof”—structures.

First published June 22, 2016, on NIST’s Taking Measure blog.

About The Author

Sam Manzello

Sam Manzello is a mechanical engineer in the Fire Research Division at the National Institute of Standards and Technology (NIST). Manzello’s current research is to understand the relative contribution of different elements in wildland-urban interface fires and to optimize data collection methods to provide foundation for mitigation of fire losses. Manzello has authored 103 publications in combustion and fire science. He serves as a reviewer for 18 archival publications in fire science, combustion, heat transfer, and fluid mechanics. Manzello has a bachelor’s degree and a Ph.D. in mechanical engineering from the University of Illinois, Chicago.