Vertical Ventilation

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Permalink Reply by Dave Stacy on February 18, 2012 at 1:58pm

Mike,

My personal opinion and luckily the view of many ladder company officers in my department is that for your standard residential house, we need to be focusing on horizontal ventilation over vertical ventilation.  Here's some reasons why I do not typically prefer vertical ventilation:

-time it takes to get to roof with tools is often slow for companies that do not perform it routinely

-time it takes to cut a h*** can be more substantial than the time it takes to take a window

-many times a company cuts a h***, it's often not even completed because they either can't punch the ceiling, forget to punch the ceiling, or the attic is too cluttered to even attempt to do so.

My opinion is that properly timed horizontal ventilation is much more beneficial for fire ground operations.  It can be timed much better with the interior line than vertical ventilation can be, and requires less people.  Especially with staffing these days, a ladder company officer can leave 1 guy to OV a window and the rest of the crew can go search, verse needing at least 2 to cut a h***.

Obviously there are positives and negatives to both, and you can't chose one or the other for every structure fire.  But, in my experience which has been limited so far compared to others, I have seen vertical ventilation attempted to be performed far more than it needed to be, even to the point of people going to the roof for a kitchen fire.

Your comment: "I also hear that v/v removes smoke to increase victim survivability.  That maybe so, but how can making the heat, smoke and fire move upwards through the house by turning the air track toward the opening you just made on the roof increase the chances for the victims?  Maybe the fire-fighters on the roof could be upstairs getting the victims out; closing doors and opening windows (behind closed doors) so as not to draw the fire toward them (we call it antiventilation - works well to shut a fire down)"

This is a good point; a fire on the first floor with a ventilation opening on the second floor, or roof in this case, clearly draws superheated gases up to the second floor.  You should check out UL's study on ventilation by Steve Kerber which goes into great details on horizontal ventilation.

http://www.ul.com/global/documents/offerings/industries/buildingmat...

Also, I plan on doing some fire simulations showing the difference between vertical ventilation compared to horizontal ventilation in the future to be posted on my website.

-Dave Stacy

www.firefightingdynamics.com

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Permalink Reply by Michael Dombroski on February 19, 2012 at 5:54pm

Thanks Dave.

I thought I might come under some fire because I realise that ventilation is high on the priority list in North America.  There are a number of reasons why we do not use the same tactics, so I'm interested in just how beneficial it can be compared with the risk in respect of residential housing.  I will check out your work on the subject.

Cheers

Mike D 

Dave Stacy said:

Mike,

My personal opinion and luckily the view of many ladder company officers in my department is that for your standard residential house, we need to be focusing on horizontal ventilation over vertical ventilation.  Here's some reasons why I do not typically prefer vertical ventilation:

-time it takes to get to roof with tools is often slow for companies that do not perform it routinely

-time it takes to cut a h*** can be more substantial than the time it takes to take a window

-many times a company cuts a h***, it's often not even completed because they either can't punch the ceiling, forget to punch the ceiling, or the attic is too cluttered to even attempt to do so.

My opinion is that properly timed horizontal ventilation is much more beneficial for fire ground operations.  It can be timed much better with the interior line than vertical ventilation can be, and requires less people.  Especially with staffing these days, a ladder company officer can leave 1 guy to OV a window and the rest of the crew can go search, verse needing at least 2 to cut a h***.

Obviously there are positives and negatives to both, and you can't chose one or the other for every structure fire.  But, in my experience which has been limited so far compared to others, I have seen vertical ventilation attempted to be performed far more than it needed to be, even to the point of people going to the roof for a kitchen fire.

Your comment: "I also hear that v/v removes smoke to increase victim survivability.  That maybe so, but how can making the heat, smoke and fire move upwards through the house by turning the air track toward the opening you just made on the roof increase the chances for the victims?  Maybe the fire-fighters on the roof could be upstairs getting the victims out; closing doors and opening windows (behind closed doors) so as not to draw the fire toward them (we call it antiventilation - works well to shut a fire down)"

This is a good point; a fire on the first floor with a ventilation opening on the second floor, or roof in this case, clearly draws superheated gases up to the second floor.  You should check out UL's study on ventilation by Steve Kerber which goes into great details on horizontal ventilation.

http://www.ul.com/global/documents/offerings/industries/buildingmat...

Also, I plan on doing some fire simulations showing the difference between vertical ventilation compared to horizontal ventilation in the future to be posted on my website.

-Dave Stacy

www.firefightingdynamics.com

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Permalink Reply by Michael Dombroski on February 28, 2012 at 4:12pm

Thanks Trevor

I appreciate your views and find them interesting.  In the interest of heathy debate, and with all the respect in the world, there are a couple of points I would like to challenge.

A well ventilated fire goes out much easier than a ventilation limited fire...

I'm not convinced that this is always the case. Non vented compartment fires can be easily extinguished with the correct water application technique.  Containing a fire to the compartment, or alternatively horizontally ventilating via a window will ensure the fire remains there and does not spread into other compartments. I've seen fires spread into the ceiling space when the roof is opened, effectively creating another compartment with fire involvement as opposed to containing to the one.

As soon as you open the front door to begin a search or a stretch, you are venting the building.  This concept needs to be understood by everyone.  Our first tactical priority in EVERY fire should be ventilation...because anything we do to that fire is VENTILATION.  Plain and simple.  The earlier we can coordinate this effort, the better the outcome will be.

I agree.  As I said, we must understand the airtrack and the effect of everything we do. Opening the door is ventilation, but I'm not sure that we do it to ventilate.  We do it to make entry, and if we are making entry into a fire compartment we should have a hose line, or be prepared to get out quickly and close the door (should we making a snap rescue).

The key, as far as I'm concerned, is to identify the airtrack and co-ordinate any ventialtion with fire extinguishment.  If we can not control the effects of ventilation should we be doing it?  I think that the most effective ventilation is direct from the compartment on fire to the outside (a window), and not via other compartments within the structure (roof voids).

With fire spread already from the basement up to the peak because of the fire stops, a well coordinated attack can often use the steam generation to chase the fire through those same channels, and out through the vent h*** in the roof that you just cut.  Doesnt always work like that, but...Vent as high as the fire is.  In a balloon house, you will more often than not have fire in the attic upon arrival...necessitating a h*** in the roof!

Certainly fire spread in balloon frames is an issue.  We also have many of these in my response area.  I have seen many fires travel up to the roof area from below.  I have not seen steam chase a fire though.  A fire goes where the airtrack, fuel and oxygen take it.  I have seen steam extinguish fires, some quite large, in un-ventilated compartments.  Steam is a very effective extinguishing medium.  I do agree that if the fire enters the roof compartment entry will need to be made into that, normally via the top, to put it out.  The limit of our v/v on residential houses is when the fire has got into that space.

All in all it's a very interesting comparison of tactics and I'm sure we will all continue to do what works for us.  I suppose my main point is that you can operate effectively and safely at house fires without venting the roof, unless necessary to extinguish fires in that space.

Thanks again Trevor, I appreciate your perspective.

Stay safe up on those roofs!

Mike D

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Permalink Reply by Christopher Huston on February 28, 2012 at 4:43pm

Good discussion guys. The best ventilation is the type you can control. Taking the roof, taking the windows for sake of taking them is really the only improper ventilation. Really great points made by all.

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