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VENTILATION
What are your thoughts on ventilation, both at work and at my vol. station we use positive pressure. we either take out the windows or open the gable ends or vents but in the last 10 years I haven't seen a roof cut, but maybee 3 times out of a couple hundred fires. And no negative pressure fans at all.
Replies to This Discussion
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Permalink Reply by Andrew on
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I think we should be proficient in all types of ventilation and use the best type for the situation at hand. In my department most of the time ventilation is an after thought which I disagree with, also we run with 2 man companies. On a first alarm assignment we have between 7-9 personnel responding depending on whether or not one of the ladder companies is responding so most of the time we use PPV because we generally can't vent the roof in time for it to be effective. If we vent the roof it is usually because we have signs of possible backdraft showng. I also think the prevelance of lightweight construction has spread some ruling out of vertical vent in the minds of some of ICs without even looking at what the conditions really are. What we do when we use PPV is the Officer has to open the vent hole on his walk around as well as taking care of the utilities while his firefighter pulls the hoses, get them charged, then they carry their irons, ceiling puller, and fan to the door, & Vent, Enter, Search, Confine, & Extinguish. The second due companies don't always get there before they go in, the pump is set up and runs on faith until they arrive and someone is directed to run the pump, etc.
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Permalink Reply by turk182 on
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we never used ppv before because we did not have a ppv fan we just purchased one and are waiting for it to be delivered but from what we have been told once the windows are out the ppv is not effective because with the windows gone you can not pressurize the building enought to get the smoke to move is this true? but we usually used negative vent. and roof vent. if any one can let me know about ppv i would appreciate it!
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You will not believe how well PPV will move smoke if it is used properly. You need an exit that is approx 75-100% of the size opening you will set up the fan at, you also need to have attack lines in place and ready to go. I like to let the fan run for about ten seconds before I go in, it will spoil you really. Training is key because if you PPV without knowing what you are doing you will sure enough burn a house down. The PPV will not be effective if all of the windows are out because it will not be able to pressurize, but you want a couple of windows out close to the seat of the fire. IFSTA Ventilation is a good reference, there is also a good book called Positive Pressure Attack, you can find it on the Fire Engineering wedsite. How did you like that price tag? In case you don't know average price is between approx. $1500.00-$2,000.00 for a PPV fan. Did you get one with an exhaust extension to keep out CO produced from the fan from being pushed into the house?
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Permalink Reply by John Kriska on
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For turk182 and one else interested in learning more about PPV. I would be happy to share information on the use of PPV during the fire attack. Please check my page on this site for my web site, go to that and check out my credibility. You can E-Mail me via my web site or use fckrisk@yahoo.com.
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Permalink Reply by Shareef Abdu Nur on
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We also use PPV, but we are also no stranger to vertical ventilation as well. For us, situation dictates. In our high rise apartment buildings, PPV is the way to go for us. As we pull up, we first look for an aerial assignment, but we are easy to adapt and overcome. But, I will say this, "Vertical ventilation helps prevent backdraft and flashover." Negative pressure is what we use for light smoke in a small area. Be safe and stay smart.
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Permalink Reply by Jenny Holderby on
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I tried to start a discussion on ventilation a few weeks ago. It went into cyberspace and I couldn't recreate it properly so I am happy to see this one being so well received & commented on.
We have a couple of guys who insist on ventilation AFTER the fact. I don't understand that point of view. If the fire has already vented, say through the roof & the windows are gone, what is the point of putting people & equipment on a roof that is already surely compromised. In one picture on this site there were probably 8 guys cutting a vent hole 3 feet from where the fire had already burned through. Can somebody tell me why?
Recently we were on scene of a structure fire where the wiring had caused a fire in the attic on one end of the home. There was a breeze way between the house and the detached garage. This covering was essentially a roof that connected the two buildings together. When I arrived, there was a lot of smoke coming out of the eaves of the garage. The roof vent was turning pretty quickly and it did appear that the fire had extended to the garage. I spoke to one of the captians after I had made a treck around both buildings. I told him that I had seen lots of smoke on the C side but there was no reflection of fire coming from the windows, there was no apparent heat. (it was a cold night so its easy to find) We discussed ventilation @ that point. Since there was a roof vent at the top and vents on each end, we decided to raise the garage doors a couple of inches. Armed with a hose line, after I had gotten on my belly to look inside not finding an apparent fire, we raised the door farther. There was a drop ceiling so we moved a couple of tiles back to allow the air to circulate. Within a few minutes the smoke was gone. We brought a ladder in & checked above the ceiling to make absolutely sure there was no fire. Another officer wanted to cut a hole in roof to vent the garage. WHY?
We responded to a home full of smoke. The source was a combination light/van in the bathroom. We left the front door open & opened the window in the bathroom. It was a small fire, mostly insulation, and was easily extinguished. There was a lot of smoke in the attic seeping from the eaves all around the house. A crew got on the roof & found the opening @ the comb of the house for ventilation purposes & to enter the crawl space (attic). The smoke vented quickly once the hole was opened making the vent wider and popped the square 12"x 12" vent in the other comb.
We reached in with a pike pole & removed the smoldering insulation. Then using PPV vented the house to clear the rest of the smoke. The officer asked why we didn't cut a hole in the roof to vent the fire. Again, WHY? All of the damage was contained to the bathroom ceiling. There was no need to make a hole when there was already a means for the smoke to exit.
I realize that sometimes you do have to make an opening for the smoke to escape from why do more damage when it isn't necessary?
I have seen firefighters attempt PPV that wasn't effective because they hadn't sealed the opening with positive pressure because the fan(s) were not properly placed.
In one situation, when firefighters "thought" the fire was out, they decided to ventilate, besides not sealing the opening & not having a large enough exit, they blew embers down the hall of a mobile home where the fire landed in the master bedroom at the end of the hallway and almost immediately blew the bay window out. The "POP!" clued them in to the mistake.
Ventilation is a technique as well as a tactic. Some departments have officers who "understand" the tactic and practice the technique and are successful with it. Improper vent practices can cause more harm than good. We really need to train better in the use of vent tactics.
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Permalink Reply by Art "ChiefReason" Goodrich on
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PPV as an offensive weapon for small fire departments?
Unless you practice, practice, practice; know building construction like the back of your hand, along with fire behavior, weather patterns, proper size up, pre-plan and fully grasp and understand how forced air affects fire, then have at it.
For my department, the "IFs" that are a part of the discussion ARE the deal breakers. So, we won't be using PPV as an offensive weapon in the near future.
I have seen the side effects and the bad effects of improperly positioned or improperly engaged PPV.
It is NOT a tactic designed for easy deployment. It's not like practicing donning and doffing an SCBA. There are many variables that must be considered/controlled in order for successful use.
People like John Kriska and Paul Grimwood have a very experienced relationship with PPV.
In fact; in Grimwood's newest book Euro Firefighter, he discusses "anti-ventilation". Check it out.
TCSS.
Art
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Permalink Reply by FETC on
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Lt2406,
We have multiple electric PPV fans, gas PPV fans, and negative box fans on our appratus and we use vertical /horizontal / or a combination of the two ventilation types at every fire. IMO hardcore PPV department's think it is the only way to go.... many agrue it helps with safety, (lack of manning needed to vent, fire up the fan and enter for fire attack, no dangerous roof operations, reduces roof collapse, etc) Hey guys, if we are operating with so few firefighters, the PPV is not your answer...
Knowing your building construction, location and EXTENT of the fire is critical and how many of us can actually predict or guesstimate wear the fire is now and what has it breached before our arrival? Regionally not everyone has balloon frame construction in their response districts. PPV is great for burning the roof off a 30's balloon frame dwelling, been there done that in the early days of hey let's use this cool new fan.
Just a thought, I have never heard the act of "vertical ventilation" expediting a flashover, or pushing fire into a void(s) or even burning the roof off a structure when it gets ahead of the brothers. If you are not sure where it is, fire up the PPV and get ready cuz the monster will show its ugly face soon.
IMHO - PPV fans are great for removing smoke from cooking, (with no fire) Many people talk about using PPV/PPA for initial attack and not needing a ladder company on the roof. As you know, it is extremely difficult to identify the exact location of the fire unless you have an early notification for a room/contents fire, or have a manned station with a very quick response to an early incipient stage fire. I work fulltime, our responses are 4-5 minutes from time of notification to the scene. The concern to others should be, arriving 10-15 minutes post notification and by then, the use of PPV/PPA will take some of the heat off the initial attack crew but where are you pushing all that heat and fire now? And if done, are you pushing good air into the attic that is above the UEL becasue the container is maxxed out? I have seen alot of youtube videos that the fan expedites the attic flashover and in certain types of structures are we expediting the roof collapse as well?
And for the brothers who say, just getting in and venting from the inside out, with hydraulic vetilation is the way to go. Well it is for the small room and contents fire but a well envolved 2nd floor fire will be impossible to push up there when "The Box" is at max capacity for heat and smoke volume above the fire (meaning the attic). Even with every window out on the upper floor, the use of PPV/PPA will only expedite flashover in the attic because the container is above the UEL or expedite roof collapse from the ensuing flashover in the attic void once fire occurs. The container is maxxed out without a place to relieve the heat and gases from the highest point in which the unburnt combustion is trapped, hence in the attic. This is why we must obtain a ventilation profile and calculate what our actions be it, PPV, PPA, Veritical or Horizontal will do for us and what it will do to the fire's behavior.
Risk vs Gain - If there is confirmation of no life safety issue, why push in, or get on the roof or even use PPV when we should start being more progressive with risk vs. gain modeling. We are not saving shit anyway, heat and smoke wreck most everything even on small fire due to the increased BTU's from the furnishings of today.
Now I am NOT a PPV hater... there is a time and place for PPV/PPA. If you were to look at using the PPV/PPA operation at certain types of occupancies or certain types of fires then yes, PPV is the answer to many un-warranted FF burn injuires. One example being a Type 1 or 2 occupancies, (high rise) fire mid level within the structure, these are compartmentalized units, not alot of places to push hidden fire into due to the type of construction. These fires are really hot. Working in an UNDERVENTILATED fire situation is not uncommon. Ask any NY guy who arrives at a fire on the 10th floor, of a 15 story building... these are killers in the hallway. Using a PPV/PPA approach can and will eliminate the heat and smoke off of the initial attack crew and push it back into the compartment of origin. Thus reducing the chances of being burned in the common hallway. That fire, that heat and smoke is ALL trying to go UP and OUT naturally, therefore it wants to come right at us HEAD-ON. In these buildings the use of PPV is not as much of a concern with the strucural design, fire spread timeline and where are we pushing contents fire as compared to a balloon frame dwelling. The use of a smooth bore nozzle in these types of underventilated fires is another tactic that the FD has control of and will dramatically reduce steam burns to our brothers as well...
Am I a smooth bore advocate? Not really, It all comes down to using the right tool for the right job. Next time you want to measure a 1/16th of an inch, try doing that with a yardstick???
Another wonderful example of great characteristics of the PPV. How many of us have charged a common stairwell with a good PPV fan in a grannie occupied high rise building that had burn't food on the stove on the 7th floor? The PPV is great for controlling and blowing the smoke right out of the occupants apartment window 70 feet above the actual fans placement... same can be done under a good fire as well.
TCSS
FETC
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Permalink Reply by BIGTRUCKMAN18 Overpeck on
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This is a topic that we can go round and round on!! But to me i feel that the situation of what your facing should dictate what tactics should be used! There are so many different way to ventilate a structure so many techniques to use whats right? Well who really knows ...what I see in our department is guys who are young ...very young with not to much experience. For these guys coming in they have been shown only a few ways usually by the book only, we all probably could agree that technology in the service has come so far forward in such a short time, that sometime ventilation can be as simple as bread and butter operations that we sometimes forget about! I love cutting hole in roofs just like many of you other truckies out here but sometimes that is not what need to be done sometimes it can be as easy as making entry and opening a window yup not much fun but effective and cost effective for the structures owner!!! Just remember is all else fails.........................................................PUNT
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Permalink Reply by Ted Mead on
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It depends on the situation and what is being removed/ ventilated!
positive pressure ventilation needs an adequate escape route for smoke or some light gasses,
but a heave gas or mist of tear gas needs the use of positive pressure and exhaust (negative pressure)
these are required to get a large volume of air moving to disperse the gasses and or mist.
most ventilation needs that firefighters encounter is smoke removal! smoke tends to be heated and will readily rise! therefore attic / roof/ gable or windows offer sufficient escape,
heavy gasses such as co2 or tear gas however do not rise readily and ground floor exhaust and positive pressure are required and will disperse them quickly.
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