N.Y.C. Fire Dept. Rethinking Tactics in House Fires Vacant houses with modern furniture will be burned in an experiment on Governors Island. One of the first tasks for firefighters arriving at a blazing home has long been to ventilate the structure - make holes in it - so that hot gases and smoke can escape. It has been this way for generations: a so-called roof man from a ladder company opens a hatch or saws through the ceiling, while other firefighters break windows as they search inside, often before the first drop of water has hit the fire. But house fires have changed. Now, spurred on by at least one grievous injury to a firefighter last year, the New York Fire Department is rethinking its tactics for residential fires, while trying to hold onto its culture of "aggressive interior firefighting" - charging inside burning buildings as fast as possible. As it is the largest municipal department in the country, its new course may well affect the tactics of other fire departments. "We're an organization steeped in tradition and we've been fighting fires for many years in certain ways and they worked," the fire commissioner, Salvatore J. Cassano, said in a phone interview. But we owe it to everybody who works for us and the people we serve to look at the way we fight fires. Plastic fillings in furnishings like sofas and mattresses burn much faster than older fillings like cotton, helping to transform the behavior of house fires in the last few decades, firefighters and engineers say. With more plastic in homes, residential fires are now likely to use up all the oxygen in a room before they consume all flammable materials. The resulting smoky, oxygen-deprived fires appear to be going out. But they are actually waiting for an inrush of fresh air, which can come as firefighters cut through roofs and break windows. Scientists and the Fire Department will conduct an ambitious experiment beginning Monday on Governors Island in New York Harbor: they will burn down 20 vacant row houses stuffed with modern furniture, to gauge which techniques work best in fighting the blazes. "Years ago you could break a window and it took the fire several minutes to develop - or tens of minutes," a fire battalion chief in Queens, George K. Healy, said. Now we're learning when you vent that window or the door, the fire is developing in, say, a minute with the available oxygen. Plastics, like the polyurethane foam used as filling in many sofas and mattresses, have drastically reduced the time it takes for a fire to heat a room above 1,100 degrees, the point at which it is likely to burst into flames, firefighters and scientists say. How flammable such fillings can be was shown in a catastrophic 2007 fire in a furniture showroom in Charleston, S.C., that killed nine firefighters. And last year, in Crown Heights, Brooklyn, Firefighter Robert Wiedmann was burned over nearly half his body in a brownstone fire that officials said fed quickly on home furnishings and an inrush of air through opened windows. The fire appeared to be confined to a rear bedroom, and firefighters expected it to be routine. But a front room in which Firefighter Wiedmann was searching burst into flames within seconds. A video posted on YouTube recorded the inferno, and a colleague's desperate bid to save Firefighter Wiedmann's life by slapping with gloves at his burning back. Ventilation is not the only basic firefighting tactic coming under scrutiny. For instance, it has long been considered a cardinal sin for firefighters to spray water on a room full of smoke with no flames. Water drives the smoke from the ceiling toward the floor, eliminating the low foot or two of visibility - and oxygen - along the floor that firefighters relied on to navigate an unfamiliar house and that survivors needed to breathe. Some chiefs within the Fire Department have come to believe, however, that quickly dousing a smoky room to cool the gases near the ceiling might be more important than preserving any smoke-free corridor along the floor. For weeks, department officials and scientists have stocked the 20 abandoned row houses on Governors Island, which for years had been used as Coast Guard housing, with purple and beige sofas and chairs, along with coffee tables and armoires - all bought from hotel liquidators.