POSITIVE-PRESSURE VENTILATION
RANDOM THOUGHTS ON…
IN RECENT TIMES the term positive-pressure ventilation has been popping up a lot in fire service conversations. “It’s great!” “It’s the new and more comfortable way to fight fires!” “What is it?” and “How do I use it?” are just some of the random comments and questions. In this issue’s “Letters to the Editor” a reader questions why we’re not hearing more about it. In beginning his feedback, I’d like to pose some random thoughts and provocative questions that I have on positive-pressure ventilation.
As a firefighter—not an editor—I’ve seen it perform spectacularly when used in the overhauling stage of the firefight. Nothing we’ve ever seen in the past removes smoke, steam, and heat from the fire area as quickly and efficiently. Areas of the structure, including attic and cellar, are rapidly purged of smoke buildup—areas that cost valuable manhours on-scene in the past. It greatly reduces the down-time of the fire service, not to mention reoccupancy time of the structure.
However, I do have some reservations on its use as an overall answer to all ventilation requirements for the occupied structural fire.
Some proponents tout its use as an initial attack procedure. Some training films show fans set up even as the first hoseline is being stretched. The point made is that the firefighter does not have to deal with as much smoke and heat as he seeks the seat of the fire and begins extinguishment. That’s fine, but that was never one of the main concerns of the structural firefighters, at least not those I worked with or have spoken with. It was for those trapped within the structure, waiting to be found.
“It makes rescues easier. We can get to the people between us and the fire quicker.” So claim those who advocate ALWAYS using positive-pressure ventilation. (This is the area that immediate PPV use makes most comfortable.) But these are the victims that are always found, in one state or another, by all interior attack firefighters. In this case, their removal is just that —a removal.
Where are the rescues? Where are the victims located that are in the worse shape, that have the least time? Where are the ones about which we constantly second-guess ourselves? That’s right — behind the fire, opposite the nozzle. They are truly trapped and getting to them is a true rescue. Their condition will certainly worsen as the nozzle stream pushes additional heat, flame spread, and toxic by-products toward them and the horizontal vent behind the fire. It’s in this location that the real rescue is made, that the most frustrations are felt when we are unable to get there before it’s too late.
The occupancy areas behind the interior fire location must be entered, searched, and the victim removed before water is started. There is so little time. Once the line is charged and the firefight begins, this area becomes quickly untenable and the aggressive, searching firefighter becomes the victim. Positive-pressure ventilation will cut down the time that this area can be addressed by the search effort, and, to my mind, cut down the time the victim that may be there has left to survive.
Unnatural fire behavior. The firefighter is a product of his training, experience, bravery, and cunning. Successful rescues—real rescues—demand that the firefighter on the fire floor, behind the fire, or above the fire be able to outguess the fire and its probable behavior. Positive pressure can force the fire to behave unnaturally. It will move through the building and any interior accessible spaces and voids, pushed by the new draft we create. Remember, once interior firefighting begins, the building is occupied —occupied by firefighters. And, firefighters ARE a life hazard who must be our primary concern.
Vertical ventilation. In buildings of three or more stories immediate vertical ventilation is a valuable and effective life-saving and firefighting tool. Mushrooming smoke and heat buildup on upper floors is reduced. Civilians within the building can move more freely or at least gain time to be found. Visibility is. increased. Firefighters can ascend stair-cases more rapidly. Are all these benefits to be abandoned so that we can exert positive pressure on the structure” and depend only on horizontal ventilation? Remember, if we “pop” the enclosure of the vertical stairshaft at the roof level, positive pressure will be lost!
Positive-pressure ventilation is a new and innovative tool. It should be adopted for the good it can do on the fireground. I would love to hear from you about your experiences with its use in your district.
