Positive Pressure... neighbours' house?

[Eno305]

Eh guys. Talking to a buddy of mine on the job and he was telling me how one of their emerging protocols is to actually pressurize the homes on each side of an involved structure. They have no problems getting the equipment on scene and no shortage of manpower... but I haven't heard of such a tactic.

Just wondering if anyone had any opinion on it? Any feedback? Success or failure stories?

[FiremanLyman]

Sort of makes sense in theory... if you PPV the adjacent exposures then heat and smoke would not be able to enter, especially if it shares walls like rowhomes or strip malls. It is like a pressurized stairwell in a high rise. Interesting, have to watch this and see if anything comes of it.

[ChiefKN]

Up in the Great White North, I imagine you'd only want to do this sort of thing in the summer... you know, that two weeks in august, where it gets over 65.

[Golzy12]

We do it from time to time. Just like doing ppv but without an exhaust point. I read something about this tactic a while back, ill see if I can dig it up.

[slackjawedyokel]

I used ppv on an exposure with a common wall. Had a crwe inside the exposure monitoring conditions at all times. Alsothere were no breeches in the wall. Kept the heat build up down,

[ChiefSquirrel]

I've seen this tactic explained in a NFA STICO class, but only in relation to row homes or attached town homes. Basically, you use PPV to pressurize the units on either side of the fire unit, with no escape for the pressure. The idea is to help keep the fire contained to the fire unit. I have not had a chance to use this tactic or see it used, but it makes some sense to me. However, I wouldn't waste time doing it, but if you're covered up in manpower and equipment, I think it would be a reasonable thing to try.

[JohnVBFD]

With regards to this tactic being used in attached and row frame houses, this concept has its roots from the Navy/Coast Guard.

As part of standard Engineering actions on the report of a fire, the surrounding fire zones, and/or spaces are set with positive ventilation (supply fans on high, exhaust fans off or slow if possible) while negative ventilation is set in the affected compartment (supply off, exhaust on high).

It is incredibly effective at keeping the smoke in the surrounding area, mainly when smoke boundries are opened up for personal access.

[slackjawedyokel]

To clarify - we had an exit vent - the intent was two fold - one to some what pressurise the exposure building - and two, to remove the smoke and heat build up (radiant heat) - I want to emphasise the common wall (masonry) was not breeched.

[enginhouse2]

Sounds like a good tactic. I've fought a couple fires in a small town square where the buildings use common walls. I believe this would of kept the fire from breeching the red brick common wall. I'd like to learn more as this is still a threat in our district.

P.S. ---See good conversation still exists here.

[RFDACM02]

Never would have thought PPV would be taken to this level: Exposure Protection? I can buy the "concept" of attached row houses, but I'd be very wary about unknown openings. If the pressure is finding one way out, it may be drawing at another point (venturi?). PPV is all about fully controlling the flow or lack of flow of air, too often we find voids and other hidden features too late. Of course as always I'm a huge skeptic of PPV in the Northeast, where significant amounts of construction allows for large voids and the climate requires occupants to regulate their inside temperature using windows, fans and closing off portions of the house. All of this make for a much more questionable path of pressurized air travel.

As for using PPV in a separate structure? I believe it'd be a total waste of resources and time. When the curtains ignite due to radiant heat, that pressurized air current will really work great!

[DeputyMarshal]

As for using PPV in a separate structure? I believe it'd be a total waste of resources and time. When the curtains ignite due to radiant heat, that pressurized air current will really work great!

I tend to agree. I'm not sure what they'd be trying to accomplish with such a tactic.

[FiremanLyman]

Never would have thought PPV would be taken to this level: Exposure Protection? I can buy the "concept" of attached row houses, but I'd be very wary about unknown openings. If the pressure is finding one way out, it may be drawing at another point (venturi?). PPV is all about fully controlling the flow or lack of flow of air, too often we find voids and other hidden features too late. Of course as always I'm a huge skeptic of PPV in the Northeast, where significant amounts of construction allows for large voids and the climate requires occupants to regulate their inside temperature using windows, fans and closing off portions of the house. All of this make for a much more questionable path of pressurized air travel.

As for using PPV in a separate structure? I believe it'd be a total waste of resources and time. When the curtains ignite due to radiant heat, that pressurized air current will really work great!

Would assume that the tactic is used in conjunction with proper PPV on the property on fire also. This would mean having the back side of the fire to be vented, so any additional airflow from the adjoining structures being over pressured would vent out the same backside vent. In theory. Never used this tactic, but for adjoining structures it does make some sense.

For exposures to a separate structure I agree, think this would be counterproductive, actually pretty risky, for once the curtains do catch on fire you have an improper PPV'd building charged with clean air.

[mikeyboy411]

I can see the theory on MFD (multi-family dwellings) and in my mind can actually see this working well. Never tried it though... Seems pretty simple and a good way to contain a fire to the occupancy of origin. Next time we are at our Tower, I'm gonna set it up and check this out.

Great post and great conversation.

[nameless]

I could see this on attached structures, similar to the fire protection systems used in many large buildings such as high rises. I can't see a use for it in unattached exposures.

[RFDACM02]

I can see the theory on MFD (multi-family dwellings) and in my mind can actually see this working well. Never tried it though... Seems pretty simple and a good way to contain a fire to the occupancy of origin. Next time we are at our Tower, I'm gonna set it up and check this out.

Great post and great conversation.

I doubt a drill tower is going to give you real world results on extension? The real hazard is the unknown openings and voids caused by occupants or contractors. Also, one failed window in an exposure occupancy changes the pressurization and suddenly you may be pulling a draft for the very small openings you were previously pushing air out of. The problem I see in general is super charging hte uninvolved area with air, when if some fire does make it in, you'd better know it and be able to react accordingly very quickly.