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A number of changes have had an impact on the fire service in recent years: reduced manning, energy conservation measures producing "tight building syndrome," increased awareness of property conservation, improved fans and heavier fuel loads of plastic producing toxic smoke. All of these factors affect one of our primary firefighting tactics...ventilation.
Ventilation can be defined as the process of removing toxic products of combustion and replacing them with fresh air. It can be...but I like my definition better. It keeps me focused on the critical nature of the process. To me, ventilation is an ongoing battle between the fire and the firefighters for control of the building. The fire is constantly pumping the building full of toxic and flammable gases. Fire-fighters must wage war against the fire, using the right weapons at the right time to succeed. Remember, this is war, "The War That Never Ends," and if you win, you save the building and avoid casualties. If you lose, you will be driven out of the building and can suffer many casualties.
Reasons For Ventilation
There are two main reasons for performing ventilation: venting to let attack teams enter and operate for attack within the structure, often called venting for fire, and venting a specific area to provide fresh air for breathing and to improve visibility while searching, known as venting for life. Unfortunately, the distinctions are lost on many, as is even the need for ventilation in the first place. You see, the universal use of self-contained breathing apparatus (SCBA) has some people thinking that ventilation is less important than in the past just because they can breathe. There are problems with this thinking. First, it totally ignores any victims still in the building. They don't have masks! Second, it assumes that the firefighters' masks will always protect them. This is not always so.
Photo courtesy of Photos Unique/Beth Cagle-Webster
Firefighters operate on the roof during a blaze that eventually destroyed a school administration building in Lake Orion, MI, on Feb. 8, 1997. Ventilation is an ongoing battle between the fire and the firefighters for control of the building.
Several firefighters have been killed in recent years when they experienced mask problems in contaminated areas running out of air, becoming entangled or having the facepieces pulled from their faces. At the scene of one such firefighter fatality, the process of "ventilation" had been undertaken, with many windows on the upper floors opened by the interior forces from top and bottom, textbook style. The glass damage was minimal...the firefighter is dead! The third problem with ineffective ventilation is the buildup of heat which results when venting is not prompt and effective. The mask protects you against smoke but not from heat.
Firefighters determining the proper amount, type and timing of ventilation must evaluate many factors before beginning their tasks. Should the ventilation be vertical (roof), horizontal (window) or a combination of both? Will natural air currents suffice or should the process of ventilation be expedited using mechanical ventilation? If mechanical ventilation is used, should it be positive or negative pressure? Should the venting be started immediately or be delayed until the hoseline has water on the fire? The answers depend on the circumstances determined during the size-up, as well as equipment and manpower constraints, and building features and the intended purpose of the ventilation: venting for fire or venting for life. The most important concept to remember, however, is that the ventilation must be of sufficient volume to win the battle with the fire.