Replies to This Discussion

Permalink Reply by Ben Waller on September 1, 2008 at 6:45pm

The basics start with building construction, reading the fire and smoke, and using thermal imaging to guage the amount of heat in the truss void, along with popping an acoustic tile to get a visual on the roof support system and how much heat/smoke/fire it is exposed to.

You also need to know if the building is sprinklered or not, and if the sprinkler system is operating.

I used to do roof work at house fires, the occasional strip mall, and the occasional ordinary construction taxpayer or mom-and-pop store fire. We knew that those buildings had some mass to the roof supports, and that we generally had 10 minutes or so to get to the roof, vent big, and bail to the aerial.

Lightweight construction, well-advanced fires or rapidly-expanding fires in big box stores, and reduced manpower to get lots of water on the fire have changed that equation.

PPV has changed it, too. If you have a couple of large-volume PPV fans, a small fire in a big box, and no operating sprinkler system, then there's no point in going to the roof.

If you're operating in old, solid, multi-story tenements and appartment buildings like FDNY and some of the other big, traditional cities do, then there's good reason to vent the roof a lot of the time. In the lighweight single-family castles, strip malls, and sprinklered big box stores where I work, going to the roof is of occasional benefit.

Our truckies put a PPV fan in the front door a lot more than they go to the roof. It's a Command decision, every time.

If the fire has autovented, there's no point in putting firefighters on the roof.

If sprinklers are operating, there's no point in putting firefighters on the roof, as the fire is probably controlled and the smoke isn't very hot.

If the smoke is light, no fire showing, no smoke in the truss void when the first engine pops an acoustic tile to take a look in the overhead, and I know the fire's location, then maye I risk it.

If the smoke is dense, dark black, and rising rapidly, I don't have lots of waterpower at the scene, and I can see siding discoloration parallel to the truss void, then not only am I not sending a vent team to the roof, I'm going defensive on the fire very quickly, because the building is close to coming apart and collapsing.

As Frank Brannigan famously said, "A building is an architect's way of fooling the roof into thinking it's sitting on the ground." I'd add that a truss void fire is Mother Nature's way of overriding the architect's trickery.

Permalink Reply by Yank2441 on October 14, 2008 at 10:56pm

The decision to get on a roof should not be made lightly but entering a building for extinguishment should not either.

If there is fire in an attic space and you don't think it is safe to go to the roof due to a weakened support system, then it is also not safe for attack crews to enter!

If however, you make the decision to enter a building with fire or heavy smoke showing from the attic area, you had better get someone on that roof as quick as possible before a colapse takes place. It is your responsibility to protect those inside and this is best done by proper ventilation.

As already posted; the first entry team should check over head as they advance into a structure. If man power permits, a truck crew can actually enter right behind the attack crew and clear ceilings as they go. If man power does not exist, then the attack crew has the duty to pull as they go for their own safety. This allows interior crews to communicate to the IC that the building is clear from the floor to the roof in that particular area.

Clearing the ceilings is especially important in larger commercial buildings where the area above hung ceilings could be 2 feet or 10 feet to the roof system above, thus hiding heat and fire that could weaken the support.

Just remember that every attic space is not a common space. This past year I saw a house where there was what appeared to be one attic but upon investigating, the attic was split up into about five different spaces. The fire ended up being in one of those spaces and vented itself even after truck crews vented a seperate attic space.

Proper ventilation does not always mean vertical ventilation. There are people out there that are totally against PPV and if you have not been trained properly and your crews have not been trained properly, these fans can act as convection ovens.

PPV is a very helpful tool in ventilation as long as it is used in the right way. You still must make an exhaust hole somewhere near the fire area to provide relief and visibility to those inside. Remember also that for PPV to really be affective, the exhaust hole should be 1.5 times the size of the PPV entry. PPV can be used in any ventilation situation as long as the fire has been some what located and attack crews have a hose line in place to knock down the fire. When I was employed with the City of Gaffney, we constantly used a PPV in conjunction with an attack line and this worked really well but we new that the line had to be in place and the exhaust hole had to be opened before that fan was cut on!

There is also a video on the web showing fire fighters sticking a PPV fan into a door where the environment was ready for a flash over and it helped the flashover to occur. So you must be familiar with the times when PPV is not a good idea. Heavy black smoke, heavy fire on one side of the house and no exterior attack to begin with, could really hurt someone.

I hope this has helped somewhat, though you may already know the above information.

Jeff Dover
Captain, Cowpens FD

Permalink Reply by Shareef Abdu Nur on October 15, 2008 at 1:09pm

It begins with building contruction, roof pitch, reading smoke(location, color, velocity), fire location, engine company status, and most important of all manpower.