Very good presentation about PPV, PPA, smoke and heat removal, steam, etc.
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Thread: Ppv & Ppa
11-07-2007, 09:53 PM #1
Ppv & Ppa
Last edited by dadman; 11-17-2007 at 12:35 AM. Reason: capitalization
11-08-2007, 05:02 PM #2
11-09-2007, 09:21 PM #3
- Join Date
- Mar 2007
- Jacksonville Fl
they never adressed the fact that 1 cuft of air adds 537 btu's to the fire. IS this not the case with PPA?
11-12-2007, 02:15 PM #4
- Join Date
- Jul 2006
Ill have to look in my notes, but the last class I took from them, they addressed that issue, and said for every X degree cooled you cut the rate of combustion in half. Again, Im not sure the numbers, but I'll look for them.
11-17-2007, 12:16 AM #5
More stuff for your PPV & PPA pleasure.
Good links within this one:
Last edited by dadman; 11-17-2007 at 12:29 AM.
11-19-2007, 09:51 PM #6
- Join Date
- May 2000
- Lincoln, NE
From their presentation, they make it sound like PPV is the cat's meow...now granted, they are advocating starting the fan BEFORE the line moves in, and you are supposed to follow the clear air. But gosh, they've run hundreds of tests and just can't find anything wrong with using ppv...then we have a video like this. Even if they had started the fan before these guys moved in (with the smoke conditions presenting at the time they started the fan), I can't help but think that causing a turbulent flashover is the intent of PPA. PPA may have been a viable solution immediately upon arrival at their training burn, but it didn't take long for those conditions to change...check out the video:
And don't rule out other forms of ventilation to get the job done.
Last edited by phyrngn; 11-19-2007 at 09:55 PM.
11-21-2007, 10:57 PM #7
- Join Date
- May 2000
- SW MO
Early in the video you see fire venting from the B side of the structure out one of the windows.
Prior to the crew entering, you see a hose team that is apparently spraying water into the structure.
Where are the vent holes? I see two, one where the fire is venting, the other where a hose team is spraying water into. One aspect of PPA is that you have to have a hole(s) larger than the hole the fan is blowing into to vent the smoke/heat. I can't see the C side of the structure, but I'm betting this isn't the case.
Fan placement bothers me. If that fan had been placed properly, there shouldn't (not saying couldn't) have been smoke coming out of the top of the doorway.
From what I'm seeing, these guys started putting 10K+ of fresh air and pressurized a structure that was already pressurized by the fire. The pressure had nowhere to go other than out the ront door and the one window that no water was being sprayed into. I really think that had they done this by-the-book, the outcome would have been different. However, this is speculation.
I will share a story that reminded me of this video (I saw the video the day before we had this fire). My career department is moving toward PPA and is pushing for the fan to be placed while the first-due officer is performing his walk-around and making vent holes. I will admit, we have not informed our guys or done enough training on PPA to just throw us into the fire (forgive the pun).
When we arrived, we had heavy, dark smoke showing from the structure; enough to obscure the road in front of the structure. While the captain was performing his walk-around, the back-end guys pulled two lines and set up the fan (I was the engineer). The captain opened only the rear door.
Fan was started and almost immediately the interior crew made entry. What they didn't see due to the heavy smoke was that there was a window about 3' from the front door that had busted out. The fan pushed the smoke right out that window, into the fan, and right back into the srtructure. Almost instantly it went to that nasty, yellow-brown color and an evac was sounded.
We left the fan in place, opened up more windows and vented the roof. Within no-time the smoke cleared the building and we were able to punch a hole in the cieling and knock down the fire in the attic and the room of origin. I will admit, the fire did flare when the vertical ventilation was established, but it didn't last long and there was an obvious improvement in the remained of the structure.
This ended up being an incendiary fire that had spread to the attic. What we learned from this is you have to be damn careful when there's a vent opening near the fan (use a second fan to cover it?) and that the vent openings have to be larger than the 1/2 the size of the fan's hole that we all learned for PPV. You also have to give the fan time to establish it's ventilation path. If it isn't doing it's job, you hav to ask "what's wrong with this picture."
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