Horizontal Venting
DEPARTMENTS
Paul McFadden’s Volunteers Corner
We discussed, in past columns, that vertical venting of private dwellings is important for two reasons. First, it limits the spread of the fire; second, because of that fact, it buys time for trapped occupants —time for us to find them. This month, we’ll begin to discuss horizontal ventilation.
Horizontal venting does not limit fire spread, in fact, poorly timed horizontal venting will not only accelerate the burning, but, in most cases, will cause additional problems for firefighters and occupants inside the structure.
How many times have you read a newspaper article that quoted the first civilian on the scene as saying, in effect, “I tried to get in. The smoke drove me back, so 1 started to break the windows. Then it seemed as if the whole house went up in flames….”?
A well-meaning neighbor, perhaps. But what he didn’t understand was that the increased availability of oxygen allowed the situation to remain as a stage 1 fire. For a free-burning fire, the only limiting factor will be the amount of combustibles it has to feed on. The fire will grow rapidly and, of course, consume everything.
We as firefighters know this and try to control horizontal ventilation to coordinate it with line placement and line movement within the structure. You might think that if the windows or other available horizontal arteries within the structure hold the fire, it might be best not to take them at all. But, like the actions of the well-intentioned neighbor, this is just as incorrect.
The fire area must be vented horizontally, for at least two very good reasons:
First, although horizontal venting allows the fire to increase in intensity, this action lets us see exactly where the fire is. It should follow that if we can see it, we can get it.
Secondly, and most essential for the interior nozzle team, horizontal venting gives the fire, smoke, and steam a place to go. I’ve said this before, and it bears repeating: If you don’t give the steam an exit, it will outflank the advancing engine company, roll over them unnoticed, and cause painful injuries. In the least case, the lack of proper horizontal ventilation behind the fire will halt and break down an effective interior attack.
Effective horizontal ventilation requires two openings, one for the fresh air to enter the structure behind the nozzle advance and another for the contaminated air and steam to exit from behind the fire (opposite the direction toward which the nozzle is advancing).
Creating the first opening is easy. We normally get the air through the door that we entered. Opening the nozzle and starting water flow will begin to pull needed air through this door. This works well as long as the door remains opened. Don’t pass unchocked doors with a handline. Likewise, never enter a fire occupancy with an uncharged line. If the door closes over the flattened hose material, you’ll not only be unable to receive effective nozzle pressure, but your horizontal opening (for air and escape) will be effectively locked. Call for water at the entrance steps.
Once the line is ready to mount an interior attack, create the second opening. Ideally, this is done from outside by breaking a window (or windows) on the other side of the fire, where the nozzle is going. This exit vent is critical. It’ll make all the difference in the world to the nozzle team and its progress. I’m sure you’ve all been told to vent when the line is in place for attack. But when is that time?
I believe that if the engine company has water, it’s ready for attack. Begin to provide proper, coordinated venting for interior movement. Start taking the windows that are appropriate. A good start, when ordered, is to vent the windows in the immediate fire area. Many times we see firefighters perform this function ineffectively. They move from window to window, breaking only some of the glass and not really providing an effective ventilation flow. Make sure that the entire window is cleared. Make a “doorway” out of it. This means removing all of the glass, screening, curtains, drapes, Venetian blinds, and the glass framing.
I place additional emphasis on the glass because of the thermopane windows that are found on today’s private dwellings —they react differently when we attempt to break them. Make sure you’re standing well to the side of them, as they sometimes burst with explosiveness. This is caused by the heating vacuum between the panes and by a difference in temperatures betw-een the inside and outside panes. (The inside sheet is hot, while the outside is protected by an air space).
Some of these windows have heat reflectors within the air space and, when broken, leave large shards of glass remaining in the frame. Occasionally, this remaining glass occludes more than half the available opening. That much restriction is unacceptable for effective horizontal ventilation. Be sure to clean the entire opening of the window frame before going on to the next one. If the products of combustion exit the new opening under pressure, the engine team needs more venting.
If that’s the case, continue to open that side of the structure until you can see or hear the hose stream.
For fires on upper floors, ladders will be needed to provide adequate horizontal ventilation. I said this before and received some nasty letters in disagreement, but I still believe it to be true. Take the ladder and slam it against the upper half of the window. Reset the ladder at the sill and ascend to remove the remaining parts of the window before moving on to the next.
I realize that some of our volunteer fire departments respond extremely shorthandedly, especially on a weekday afternoon. Don’t forget the pump operator. Once his water supply is assured, his supply pressure adequate, and his hoselines charged, he can help. Feeding hoselines, butting ladders, and moving tools and other equipment will still keep him close to his primary responsibility— the pumping engine. These additional assignments can be turned over to arriving personnel. Initially, we need more hands than we have, not a baby-sitter.
Horizontal venting is for the nozzle team. It allows them to move aggressively and more rapidly toward the fire. Give it to them and things will run more smoothly. Eighteen years ago, when I was going to probie school, there was a prophetic sign on the smokehouse door. It read, “Vent and ye shall live.”
