January 1, 2006 Firefighters usually don't aim hydrants at smoke, to avoid producing steam that can come back and burn them. But smoke sometimes contains dangerous, flammable gases. Some U.S. fire departments are now experimenting with brief bursts of water on the hot gasses, to cool them down and reduce the risk of explosion. Since it was adopted in Sweden, the technique has cut firefighter fatalities in half.
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GRESHAM, Ore.--Every year dozens of firefighters in the United States die fighting fires. Explosions, back drafts and flashover fires can trap them inside buildings. Now, a new method of firefighting aims to change that.
Engulfed and devoured by flames, within seconds an inferno could surround and overcome even the best firefighters. Edward Hartin is one of the first people in the United States to teach 3D firefighting -- a method that looks not only at flames, but also the flammable gasses they create.
Edward Hartin, a training and safety battalion chief at the Gresham Fire Department in Ore., says, "The traditional wisdom was: Don't put water on smoke, keep your nozzle closed, crawl under the smoke layer, get to the base of the fire, and put water on the fire."
Hartin's firefighters still use a powerful stream of water once they get to the flames, but first, they shoot short bursts of water, creating a fog. "You're providing a buffer zone, in essence, between the firefighters and the fire," Hartin says. Without that buffer zone the gasses can ignite.
The process starts even before they enter a burning building. Hartin's firefighters start their "gas cooling" before they enter the building. Once inside, they continue the short bursts until they get to the flames.
Mark Robison, a lieutenant at the Gresham Fire Department says, "The reason why they're not putting a lot of water up into the heated gasses above them as they're coming in is it will convert to steam and come down on top of them."
Critics fear gas cooling will actually create more steam burns -- but after Sweden adopted it in the 1980s the death rate from extreme fire behavior was cut in half.
Another benefit of this method is if you use less water to put out the fire. It also means less property damage. Fire departments in Oregon and one in Virginia are starting to use these techniques. To find out more go to www.firetactics.com.
BACKGROUND: A new strategy for combating fires has been embraced by firefighters in Sweden and Great Britain, and is starting to gain acceptance in the U.S. Called 3D firefighting, the tactic takes into account not just the structure of the fire, but also the gases that fill a room. Firemen can gauge a blaze with thermal-imaging equipment and then use split-second pulses of fog to attack to control and extinguish the blaze.
THE OLD WAY: In the U.S., firefighters are trained to kick down doors and douse flames with water pumped through massive hoses. One of the oldest rules in the business is, don't put water on smoke, especially if firefighters are nearby, because the water will turn to steam and cause burns. But fires can now project their energy much farther from their cores. This makes them more dangerous and difficult to extinguish.
THE NEW WAY: Bursts of delicate fog cool the gases and contain the fire. The water is broken into tiny droplets and deployed in extremely brief bursts, so instead of turning to steam, the moisture's expanded surface area will cool the gases in the smoke. Then firefighters can move closer to the blaze -- instead of ducking for cover -- and once they are close enough, revert to the old method of smothering the blaze with a massive application of water.
GASSY ELEMENTS: House materials inside and out have changed dramatically over the last three decades -- most are now made from synthetic materials rather than wood or metal. So today's blazes produce two to three times as much energy as a typical fire did in 1980, and most of that energy is released as flammable gases. The invisible gases produced in a fire can be much more dangerous than the flames, especially in enclosed spaces. Newer buildings are well insulated and tightly sealed. That means gases in newer buildings can become superheated, flammable and highly mobile. The result is extreme fire behavior, marked by life-threatening backdrafts, flashovers and gas explosions. Scores of firefighters die each year because they use old outdated methods against this volatile mix of physics and fire gases.