Fire engineers at the National Institute of Standards and Technology tested the effect of wind-driven fires and developed related firefighting tactics for use in residential and high-rise buildings. Wind-driven fires create dangerous fire conditions that penetrate firefighters’ turnout gear and lead to loss of life, said Dan Madrzykowski, a NIST fire protection engineer.

Researchers at NIST, a non-regulatory agency under the Department of Commerce, initially began to study how firefighters died of thermal shock in high-rise fires. In each case, burn injuries weren’t necessarily inconsistent with life.

“They weren’t that bad,” Madrzykowski said. “But yet there was an extreme heat condition they were overcome by, and it seemed to happen very quickly. We needed to get a better understanding of why that happened.”

Madrzykowski said researchers conducted a series of experiments to study the effect of wind on high-rise fires or buildings with seven or more floors. He said eight experiments were conducted at the agency’s Large Fire Laboratory.

Tests demonstrated that a fire expands when wind and an open vent are present. Madrzykowski explained that wind conditions push hot gases and smoke from the apartment of origin into public corridors and stairwells. Typically, a firefighter on scene opens a door, or a series of doors, to create a vent path through the structure. Now, the opened window is the inlet for the fresh air. As a result, flames blow horizontally and force their way through the apartment into the corridor.

Usually, the firefighting environment has hot gasses on top and a cool layer on bottom. That’s not the case in wind-driven fires, Madrzykowski said. Sometimes they remain as flames creating a blowtorch effect — which some firefighters have described. Other times, fires still don’t have enough oxygen and exist as super-heated gases.

“It’s taking these well-mixed hot gases and basically creating a near uniform temperature from floor to ceiling,” Madrzykowski said. “So there’s no way for these firefighters to get low and get out of the hot gas flow.”

During the test, the flow path’s temperature reached at least 750°F, Madrzykowski said. Because the wind is blowing, super heated gases flow over the turnout gear. The gear is designed to absorb the heat but it has a finite limit. The next layer affected is the firefighter’s skin.

“The temperatures we saw in our experiments would have been lethal, even to a protected firefighter,” he said.

Researchers collaborated with the Fire Department of New York to create a wind-driven fire in abandoned buildings on Governor’s Island, N.Y. The live tests confirmed laboratory findings.

What researchers found prompted NIST to release several recommendations about wind-driven fires. First, Madrzykowski said wind awareness during a size up is crucial. “To the best extent you can, you want the wind behind you,” he said.

Second, control the flow path. The absence of a flow path prevents wind-driven fire conditions throughout the building. Be aware of which windows may fail, which windows are opened and to try and maintain control.

Equipment and tactics also are used to prevent wind-driven fires. Madrzykowski said use a small amount of water at the fuel source or initial burn room that caused the window to fail. In a high-rise, a high-rise nozzle is used. Firefighters use the tube from the floor below by opening the window, placing the nozzle outside and throwing water overhead. The wind helps push the water into the apartment to cool the hot gases and removes the wind-driven fire conditions, he said.

Another strategy is to deploy wind-control devices, Madrzykowski said. Firefighters deploy heat-resistance material from one floor above the fire over the window on the fire floor in order to block wind. He said it diminishes the velocity of the hot gasses through the space. It also blocks oxygen and smothers the fire.

“You drop the temperature throughout the fire floor at least by 50% within 60 seconds or so,” he said about the technique.

A third technique is the use of positive-pressure ventilation fans. They do an excellent job of pressurizing the stair and stabilizing it so firefighters have a safe refuge or a place to start their fire attack, Madrzykowski said.

“They don’t create enough pressure to overcome the wind-driven fire condition,” he said. “But when the other devices or techniques are used — the positive pressure can be affective with the blowing the smoke out of the corridors and adds cool air behind the firefighter’s back to work with.”

NIST now offers its finding on a set of DVDs. They are free of charge to public-safety agencies for firefighter training. E-mail Madrzykowski to request a copy.