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PPV and PPA
I did an internet class yesterday at the fire station on PPA (positve pressure attac). I have been around the fire service for many years and alot of this class goes agianst everything I have learned over the years. I would love to implement what I learned but I would like to know if anybody is activly using PPA and how is it working for you.
Replies to This Discussion
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Permalink Reply by John Kriska on
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Sorry I did it again with this miserable Microsoft Office 2007. Attached is the Walter Cover document in Word 97.
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WalterCover.doc, 79 KB
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Permalink Reply by Kriss Garcia on
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Personally I am not to worried about not covering the entire door. As a matter of fact having a little space above the door to see if smoke or flame com back towards the blower is a good indicator of whether or not you have enough of an exhaust,,,remember the negative area outside is much more important as the fire will seek that location, than the positive area that you are creating.
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For a moment place yourself in a structure that is on fire. You are unconscious,,,,would you rather have no ventilation or have the products of combustion removed as fast as possible. The limit of the exhaust is what causes the increase in heat at the floor level. Even when this does occur the O2 level increases and the CO level decreases. Also this heat is dry not wet as is the case when water is placed on the fire with inadequate ventilation. When this happens thermal injury increase three times. CO increases dramatically and O2 levels decrease....Personally I would rather not have a crew outside being cautious while they made there way to where I am located awaiting to be burned, have my O2 level decreased only to be replaced by higher levels of Benzene and CO.
If it were my kids in the building I know that the only chance they have is a quick rescue and removal of the lethal products of combustion ahead of the hoseline.
we have interviewed over 6000 firefighters and have determined that the chance of making a live rescue of a person in the area of fire after water application is less than 1%.
We have also done hundreds of live burn evaluations where our findings have all been affirmed.
So,,,,,,
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Permalink Reply by Art "ChiefReason" Goodrich on
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Believe it or not, I have been doing some reading and I have some questions:
Is a thermal imaging camera used in conjunction with PPA or does the interior atmosphere clear to the point that a TIC isn't necessary?
In the NIST study that I read, it states there should be a one to two minute delay of the hose team attack. This is to allow the blower to adequately clear the involved room. Will a larger blower decrease this "delay" time?
In the same study, it stated that flames extended up to six feet out of the window. As an example, if you are in rowhouses, will fire impinge upon another, nearby structure? Is this covered by an exterior hose team or would a vertical opening be considered?
In lightweight construction, would the blower not be used during initial attack?
I'm trying; really, I am.
Thanks.
Art
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xchief22:
Let me see if I can answer your questions:
TIC: A TIC allows for "sight" through smoke because of no visibility. If PPA is done properly, it provides visibilty. This is why fire attack and/or search and rescue operations are speeded up as compared to groping around in the dark Even with a TIC the process is still slow as compared to actually having visibility because the smoke ceiling has lifted. As the Fire Chief you must decide whether a TIC is needed.
NIST Report: Remember these folks are testing the use of PPA in a high rise building. Due to the distance the pressure must travel to do the crew any good, that time is extended as compared to a normal residential building where we recommend a wait of about 30 seconds. Why this waiting period? It allows PPA to take control of the interior environment, raise the smoke ceiling, start pushing the products of combustion out of the building and reducing the temperature thereby opening the path to the fire for the attack crew to follow.
Fire extention: This must be a consideration of the Officer when they size-up the situation. If the possibility exists that using PPA would extend the fire to the building next door, then I would suggest you not use it, however, if adequate personnel are available then an exposure protection line would be in order. This situation must be covered in any PPA training.
Lightweight construction: I see no difference in using it in any type of construction as long as you can provide an adequate exhaust opening and pressurize the building.
Allow me to expand on lightweight roof supports because I think it is an extremely important subject. The system I used as an active Fire Chief was a four step size-up method. 1) A Pre-Plan Size-up 2) Windshield Size-up 3) Exterior Building Size-up and 4) Interior Building Size-up. My Officer was provided a printed computer generated pre-plan of any commercial building in our city. Enroute they scanned the pre-plan, one of the bits of information they were looking for was what type of construction held the roof up. Upon arrival, a brief windshiled size-up was reported, then after disembarking the Officer performed an exterior building size-up. PPA would be set up and ready to go if the Officer elected to use it. Once the crew entered the building the Officer was required to stop them and keep them in the safe zone while the Officer did and interior building size-up; making observations on current conditions, if they did in fact ventilate the building was it working and if the pre-plan showed lightweght roof supports, was fire attacking the roof supports. If they answered yes to this last question, they were not allowed to proceed beyond the safe zone but using a straight stream, attack the fire from that position. This procedure all paid off for us early one morning in a restaurant fire with roof collapse, no one hurt and no one killed, they were all in the safe zone when the roof came down. This incident was the subject of an article published in Fire Engineering by my collegue Jerry Knapp of Rockland County, NY. I know this has nothing to do with PPA but since you mentioned lightweight construction I thought it would not hurt to address the issue.
Hope this helps..
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Tom:
Flashover or SMOKE EXPLOSION?
From the color of the smoke, it's hard to say.
But, as you approach flashover temps (approx. 1000 degrees), the goal should be to immediately reduce the interior temp. If water is readily available, I am at the door and giving it a couple short bursts aimed at the ceiling.
It will reduce the heat.
I am afraid and this is just my uneducated opinion, that, if you introduce a blower, remember that the temperature GOES UP before it GOES DOWN.
I would not deploy the fan at that point. I would go with natural vents.
IMHO.
Art
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Tom:
I'm still shaking my head.
Did it seem like there was a lot of jacking around? The guy with the flat axe. Wasn't too motivated, was he?
In this case, it appears from the exterior that it is cinder block construction? Chimney effect, if so. Heat is held in and will want to go up.
Judging JUST from the video and the imbedded time, I'd say that PPV would have been appropriate.
However; with fire in the rear, it had already vented to some degree.
I still think that I would have instructed the pipe to hit it with short bursts.
IC seemed concerned more with what they could see and not with what they couldn't see.
What's your take?
Art
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Let me send the link here to John Kriska. I know he's on the road, but he could give his observations, I'm sure.
Art
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Permalink Reply by David on
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I have used PPV in the UK for many years. Carried on first line pumps (engines) it is one of the first items of gear I would ask for as firefighting entered its final stages. Once safe to do so, I have often walked into a building within seconds of PPV starting up. The building being almost clear of smoke and allowing me to enter without BA.
Using closed and open doors to direct the PPV, the area involved can be cleared quicky and efficiently. This allows BA to stand down and creates a comfortable working area free from smoke and more importantly, heat for cleaning up etc.
However, it is important to implement at the right time and as you say it could be dangerous if started up too early.
We in our Brigade were only using the PPV as post firefighting or defensive mode although some brigades use it also as intermediate and offensive PPV.
Training is essential before using the fans but I am convinced that when used correctly, PPV is an essential part of modern firefighting in buildings.
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Permalink Reply by Mike Sullivan on
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David,
Although I agree whole heartedly with you assesment that setting up PPV properly can clear a structure of smoke, as well as making overhaul a lot quicker and easier. One small issue from your post concerned me though.... you mentioned being able to enter structures without the use of BA due to the fact that it was clear of smoke. One issue that I have seen mentioned in numerous texts is that the fan unit itself runs on a gasoline engine, thus it's exhaust contains Carbon Monoxide (CO), the fan is located right in front of the engine, blowing this colorless, odorless, yet highly toxic gas into the structure. I personally have never measured the CO levels generated by the engine, so I dont know if this is a real problem or only a "textbook theory", but I would suggest checking your unit(s) to determine.
To evaluate your particular unit, simply find a room with a 0ppm CO reading via a multi-gas meter and then run the fan for a period (15-30 minutes should be enough). Leave the gas meter in the room while the fan is running and see if the level of CO in the room rises, and how quickly it does so. Checking the meter every 5 min should produce a good "response curve" for the study.
If you (or anyone else out there) does this test I would be very interested to see the results, please include the Make and Model of the unit along with the result...... perhaps some brands give off more CO than others....
Just my thoughts..........
Be good, stay safe
Sully
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Yes, I would have used PPA correctly which in this scenario boiled down to making an adequate exhaust 2-3 times the size of the vent point, waited a few seconds for the environment to clear and then make the attack.
Information from the firefighters who were inside it appears that after the flash conditions were not as bad as they appeared from the outside. Bad tactics may have caused this, but the blower made the conditions survivable because it self vented....
Just my opinion
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Information on this site from some (not you) should be suspect. You either have ventilation or not. Having products of combustion showing from some areas does not mean you have ventilation,,,,,The fire coming back towards the entrance over the top of the pressurized area is a sign that should scream to anyone who is giving advice on tactics. THEY DID NOT HAVE VENTILATION!!!!!!!!!!!!!!!! PPA needs to be working prior to sending anyone in,,,if not go ahead and attack fires as we have for the last 200 years,,,,
Thanks
Kriss
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