Taming the Flames
The third advance that has the potential to change how fires are fought is also the least sophisticated of the technologies. Its origin lies in an incident that occurred nearly a decade ago.
On December 18, 1998, three New York City firefighters died while fighting an apartment fire on the tenth floor of a building on Vandalia Avenue in Brooklyn, New York. They had been searching on various floors for an elderly woman they thought was still inside, although she had already been evacuated.
As they made their way through the building, the firefighters were engulfed by a fireball that streamed out of an apartment into the hallway where they were, and toward an open apartment door at the end of the hallway. The temperature spike caused by the fireball melted the firefighters’ oxygen masks off their faces. They died soon after of smoke inhalation and burns.
This phenomenon is known as wind-driven fire. It can occur in any structure, though it is more prevalent in high-rise buildings. NIST’s Kerber, along with his colleague Dan Madrzykowski, has studied what happened at Vandalia Avenue in hopes of understanding the wind-driven- fire phenomenon and how to combat it.
Part of the problem is that firefighters are trained to meet the fire—which firefighters refer to as the dragon—head on. It’s part of the mystique of the business, says Jerry Tracy, a Fire Department of New York battalion chief. Nevertheless, he says, “We’ve lost everytime,” referring to wind-driven fires.
The goal of the NIST research is to find alternative strategies of attack that can allow firefighters to battle structure fires under wind-driven conditions while minimizing the risk to their lives.
What Kerber and Madrzykowski discovered is that it’s all about pressure. When an opening is created in two different locations in a structure—whether it is by the fire service opening an evacuation or ventilation path, by people fleeing their apartments, or by windows breaking due to the heat—fire can hurtle from the high-pressure opening down along its low-pressure path. This can have horrific consequences for anyone caught in that path, especially for firefighters, as the Vandalia Avenue incident showed.
Those three firefighters died because a sudden shift in pressure occurred inside the building when the window in the fire apartment broke. As the window failed, the wind rocketed the fire out of the apartment like a blowtorch, down the hallway, and towards an apartment that had a door and window open. The hallway became, in effect, a chimney as the fire flashed through it, according to Grant, whose foundation also sponsors research into wind-driven fires.
“When you get a high wind, and there are a number of open doors between the fire and where the fire wants to go,” says Kerber, “then unfortunately, firefighters have found themselves in that path with essentially no protection, nothing to do.”
To gain a better understanding of this natural phenomenon, NIST partnered with the fire departments of Chicago, New York City, and Toledo, Ohio, to conduct wind-driven-fire experiments. The experiments used abandoned high-rise buildings packed with flammable furniture—what Kerber and other fire experimenters call “fuel packages.”
They then created openings that would cause the fire to rush from a high-pressure area to a low-pressure area, simulating conditions firefighters face when they fight real wind-driven fires. What they discovered both surprised and scared them.
“Conditions change even more dramatically than we realized,” says Grant. “The temperatures immediately exceed, in literally seconds, well beyond what the gear is capable of withstanding. So if they don’t get out of there within 10 seconds, it just becomes too much.”
The experiments led to the development of solutions as brilliant as they are crude from a technological standpoint. All it takes is a few fans, some crooked nozzles, and flame-retardant blankets to reduce the unpredictability of wind-driven fires. The results, says Tracy, “have been profound.”
Positive-pressure ventilation. One solution is called positive-pressure ventilation (PPV), which uses specialty fans manufactured by Super Vac and Tempest to flood a certain space, such as a stairwell, with air, says Kerber. “They’re designed to move a heck of a lot more air than your typical Home Depot fan,” he says.
By positioning these fans of varying sizes a few feet away from a doorway and placing them strategically throughout a building’s stairwell, the air blown into the stairwell seeks to equalize, if not increase, the air pressure in the stairwell as compared to the air pressure on the fire floor.
The first fan should be positioned at the base of the stairwell. If needed, another fan should be positioned not more than two to three floors below the fire floor. Additional fans may be needed every ten floors, depending on the building height. This tactic prevents fire and smoke from entering the stairwell, creating a safe haven for refuge and a means of evacuation during a fire for both firefighters and civilians.
PPV also allows firefighters to extend their hoses into the fire hallway from the stairwell and begin pumping water into it. Fighting the fire safely from the stairwell, they no longer have to expose themselves to the risk of a wind-driven fire event.
Pressurized stairwells also allow firefighters to reach each floor of a fire without using up precious oxygen from their air packs, crucial in a high-rise fire. Air packs only provide 11 to 15 minutes of work time for firefighters, says Tracy, and an additional six minutes for evacuation.
Many firefighters, Tracy explains, have to “take the feed,” which means taking off their mask before they evacuate the structure, because they outlasted their oxygen supply. This practice causes long-lasting damage to firefighters’ health.
“That’s why we’re dying young,” Tracy notes. The extra time provided by PPV-created refuge areas could help alleviate this problem.
At the NFPA annual World Safety Conference and Exposition in Las Vegas this June, I watched as Kerber showed video of the PPV experiments to a room full of fire stakeholders, mainly firefighters. The video showed black smoke pouring into a stairwell from an open door leading to the fire floor. The smoke obscured the firefighter who was hunkered down on the stairs. Suddenly, the fans turned on and the smoke retreated back through the hallway door, seemingly wretched back by a supernatural force. Once the stairwell pressure rose to meet that of the fire floor, a “pressure barrier” was created, says Kerber, which acted as an invisible force field that kept fire, heat, and smoke out of the stairwell.
High-rise evacuations have always posed problems. Many impractical solutions have been proposed—such as slide chutes and parachutes—says Chief Bobby Halton, editor-in-chief of Fire Engineering Magazine and a member of the International Association of Fire Chiefs.
By contrast, Kerber and Madrzykowski’s work offers a simple solution. As the tests in Chicago, New York City, and Toledo prove, firefighters using PPV “can rapidly create a tenable environment for people to escape in” without any added or unnecessary risk, says Halton.
High-rise nozzles. The second tool firefighters demonstrated during the NIST experiments was an assortment of high-rise nozzles. Crafted by the FDNY’s Research and Development Department, the nozzles are shaped to allow a firefighter to send water at different angles, rather than straight ahead as is the case with traditional fire hoses. This configuration allows firefighters to safely battle a fire from the window below the source of the blaze.
Consider a case in which a fire erupts on the tenth floor of a high-rise apartment building and firefighters determine that wind-driven-fire conditions present a risk. Rather than go to that floor, the firefighters could go down one floor, find a window that offers a shot at the fire, break a window in the apartment where the fire is located, and shoot water up into the fire.
The first-floor-below nozzle has a 60-degree angle so that a firefighter can place the nozzle out the lower-floor window and spray water into the apartment above through that window. There is also a second high-rise nozzle that is equipped with a hook that a firefighter can latch onto the windowsill above before releasing water into the apartment. Either way, the firefighter can safely battle the fire without accessing the fire floor.
“Everybody realizes this is a nozzle to be used when you can’t meet the dragon head-on, because the conditions are so severe,” says Tracy. Presently, 16 engine companies have been issued the high-rise nozzles.