ON-SITE @ FDIC
Blowin’ in the Wind
Recent NIST research is changing fireground tactics
By Shannon Pieper

If you attended Dan Madrzykowski’s seminar today at FDIC, “Wind-Driven Fires in Structures,” you might have left feeling like some of the tactics you were taught in the academy are under question. Attack from the unburned area first? Maybe not. Don’t push the fire with your stream? Maybe it’s not the water that’s pushing the fire. Oh, and did you remember to consider wind speed or direction before you planned your attack? But this is a structural fire!

All of this could make your head spin, if it wasn’t based entirely on hard science. Madrzykowski, a fire protection engineer for NIST, is on the leading edge of fire science research. And he’s remarkably adept at explaining how this research is changing tactics on the fireground.

Note: For those of you who don’t have high-rises in your area, don’t think the information from today’s class doesn’t apply. Madrzykowski notes that although the research initially began with high-rises, subsequent studies—as well as anecdotal evidence from chiefs around the country—have revealed that wind-driven conditions can exist in almost any structure.

Size-Up & Flow Paths
When I spoke with Madrzykowski last month, he mentioned that one of the main objectives of his class was to get firefighters and company officers thinking in different ways about how fire travels—which is affected by the conditions outside the structure (wind) as well as forces within it (fire generated flows).

“We’re trying to get people to consider the wind in their size-up,” Madrzykowski says. “Personnel trained in hazmat always consider wind as they’re approaching the scene. For structural firefighters, it might be in the back of their minds, but we’ve seen a number of firefighter fatalities where wind wasn’t considered but was a factor.”

Another objective: To get firefighters to think in terms of flow paths within the building. “When you look at LODDs, even cases that are not necessarily wind-driven, you realize that the worst place for a firefighter is between where the fire is and where it wants to go,” Madrzykowski says. “The flow path can be created naturally, such as by a window failing, or by the actions of firefighters as they vent the structure.”

NIST’s research is also beginning to question the adage that water should be applied from the unburned areas with the structure, so as to avoid pushing the fire to unburned areas. “If the wind is already driving the fire, there’s no concern about pushing the fire with the hose stream,” Madrzykowski says. “Putting water on the fire from the exterior can be a great way to achieve knockdown before starting interior operations.”

Nozzles & Curtains
As you can imagine, new research produces new tools that attempt to address the problem. NIST has partnered with FDNY and the Chicago Fire Department (CFD) closely throughout the wind-driven fires project, and their efforts were supported by the DHS Assistance to Firefighters Research Grant Program and the U.S. Fire Administration. Now, FDNY and the CFD are leading the way in developing tools to combat wind-driven conditions, including wind-control devices and high-rise nozzles of various shapes and configuration. (Click here for a related article.)

Madrzykowski notes that FDNY has settled on four different tools for wind-driven fires:
1. A wind-control device called the blanket, which is carried by the squad;
2. A smaller curtain, about 6 x 8 feet, that can be deployed by a single firefighter, that’s carried by the ladder companies;
3. A high-rise nozzle; and
4. Positive pressure ventilation (PPV) fans

“The CFD is moving along in the same direction,” Madrzykowski notes. “They have high-rise nozzles and wind-control devices that they’re experimenting with. So we’re starting to see some use of the new technologies as a result of this research, and we’re also seeing a lot of interest in our findings from around the world.”

Burning Hotter?
If you’ve read more than one article in a fire service magazine lately, you’ve no doubt heard the mantra that fires are “burning hotter” than they used to. I asked Madrzykowski to clarify what this means.

“Most people think flame temperature when they talk about how hot fire is,” he says. “Flame temperature, no matter the material or the amount, is between about 1,000 and 2,000 degrees F. It doesn’t vary too much. What does vary significantly is the amount of energy that is given off by the fire. One candle has a heat release rate of 80 watts and a flame temperature between 1,000 and 1,500 degrees F, depending on the area of the flame where the measurement is taken. Take 10 candles, and the flame temperature won’t change, but the heat release rate is going to go up by a factor of 10.”

Therefore, energy is what firefighters should consider when they’re evaluating tactics. “If you have a mattress fire burning under a poorly ventilated condition, you have a lot of hot gases in the smoke that store fuel and energy,” Madrzykowski says. “Think of the fire triangle—the only thing that’s missing is the oxygen to get it burning. So you need to think about how to break the fire triangle—maybe you cool the gases off as you enter, or maybe prevent it from getting an additional surge of oxygen. You don’t want to put the PPV fans up after the firefighters are in there; you don’t want to vent additional windows when you have hot, black smoke coming out of the building.”)

Next Steps
Even as he’s busy sharing the tactical implications of NIST’s research on wind-driven fires, Madrzykowski is hard at work on the next stage. “We just finished burning 20 townhouses in Chicago in 2 weeks—bread-and-butter fires,” he says. “The structures have identical footprints and are loaded with similar furnishings, which allows us to look specifically at how ventilation changes fire behavior.” The research will help further clarify the issue of whether introducing water from the exterior pushes the fire.

A similar effort by UL and Steve Kerber involves a two-story colonial and a single-story ranch home. “We’re hoping to tie together our data sets so we have data for three different structure types for the fire service,” Madrzykowski says.

The next step: Create a computer-based firefighter simulation using these tests as validation. “The engine company can use the simulation to practice size-up and real-time, physics-based tactics,” Madrzykowski says. “They can see how the fire will respond to size-up, venting windows, opening doors.”

It’s not exactly “Call of Duty,” but I bet that’s a simulator most firefighters will want to try their hand at.

For more information on the NIST wind-driven fire research, visit www.fire.gov. If you’d like a copy of the wind-driven research DVDs, email Dan Madrzykowski at daniel.madrzykowski@nist.gov.

Shannon Pieper is deputy editor for FireRescue magazine.