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The damage that results from our efforts should be commensurate with the amount of damage the fire is causing and the extent of the life hazard. If the fire is a low-intensity mattress or other smoky, low-heat fire like food on the stove windows should be opened, not broken. Mechanical ventilation is often beneficial in moving this cool smoke and poses few of the dangers possible when using fans during working structural fires. Window venting is the most suitable type of ventilation for most fires in houses and similar-size structures which have high window-to-room-size ratios. Window venting is very quick and relatively easily performed, and can be targeted to specific rooms. When interior forces are able to operate in the building, they can evaluate the conditions to decide to vent the windows. In the past, a guide I used stated, "If you can stand up long enough to manipulate the locks, raise the windows. If you can't stand up that high or for that long because of heat conditions, it's time to take the glass." While this is still a good rule of thumb, a few additional points should be made.
First, you must have an idea of what progress fire control and search efforts are having. For example, if the fire seems to be under control and the primary search is complete and negative (no victims found), you may want to raise the windows instead of breaking glass, even though the area is moderately warm or even hot. Con-versely, very dense smoke conditions present when there is a strong potential for either locating a victim or fire extension justify breaking glass even in the absence of extreme heat.
The second factor to consider when deciding whether to break glass or not is that conditions are likely to worsen before they get better. Venting not only provides fresh air to trapped victims, it improves conditions for firefighting, leading to earlier control and less likelihood of firefighters getting disoriented or trapped if hoselines are operating on the fire. Breaking glass provides double the window-opening area that raising double-hung windows does. Since these are the predominant windows present in the majority of residential buildings, firefighters must be prepared to break glass if conditions require. The lives of occupants, as well as firefighters, hang in the balance.
Breaking glass, of course, is not something that can be reversed once it has taken place. Firefighters must properly time their ventilation efforts. Venting too early will allow the fire to extend, while delaying ventilation will subject firefighters to unnecessary punishment from heat. Generally, venting for fire should take place just as the hoseline begins its attack. This is best coordinated via radio. A member of the attack team should give the word to "take the windows" just prior to the nozzle team opening the nozzle. If radios are not available, the person doing the vent should wait until the sights and sounds of hose stream operation steam, and fire knockdown confirm the line has indeed begun operating. One exception to this sequence is made in the case of tightly sealed areas, typically glazed with double- or triple-pane energy-efficient windows. In this case, the sudden admission of oxygen as the attack crew enters can have catastrophic results; sudden rapid fire development or even backdraft are possible. When energy-efficient windows are encountered, window venting should be undertaken as soon as possible, while the attack team is in a safe area, preferably behind a closed door. If this is not possible, it may be desirable to delay venting until after the hose stream has thoroughly cooled the fire area.
One type of ventilation that should never be delayed is vertical ventilation. Vertical ventilation is critical in larger, multi-story buildings, such as apartment houses, schools and office buildings, which have stairways that serve as the occupants' primary escape route. At house fires, vertical ventilation is not a primary tactic because of the time and effort required to reach and cut through the roof material and the limited benefit to be gained if the fire is on a lower floor. In houses, the windows usually are sufficient vent points, given the relatively small areas and fire loads involved. Larger buildings have relatively larger floor- area-to-window-size ratios, higher life hazards and often heavier fire loading. In addition, they typically have stairways that go all the way up through the roof, ending in a small stairwell structure called a bulkhead, or are provided with glass skylights over the stairs to let sunlight in. These features make vertical ventilation at these structures far simpler and faster than cutting the roof at a house fire. Firefighters merely have to force open the door on the bulkhead or break or remove the glass in the skylights to accomplish the job of vertical ventilation at these structures. This critical task must begin immediately since the stairway, which dozens of occupants may be using for escape, also is the fire's chimney, resulting in rapid spread of smoke, heat and fire to upper floors. Vertical ventilation prevents mushrooming on upper floors.