Fire Engineering Training Community

Where firefighters come to talk training

Hi all

I'm trying to gain more understanding of the value of vertical ventilation in residential structures, specifically single unit dwellings or normal housing.  We simply do not do it, and have never done it until after the fire has been knocked down and fully controlled (if there has been extension to the roof void).  It is more a part of our overhaul than anything else.  I fully understand and appreciate the value of v/v in large structures to prevent horizontal fire travel and to relieve conditions for interior teams.  I also understand the value of venting above stairwells in multi-sorey buildings and defensive roof ventilation where there is a common cockloft.  We will do these things when necessary.

What I'm having trouble understanding is the value of putting fire-fighters on the roof of a house and cutting holes in it.  Ceilings are not normally much higher than the tops of windows and I can't see why well co-ordinated horizontal ventilation of the fire compartment is not sufficient.  I've watched many videos of this practice and all I ever see is a fire that appeared to be contained make its way up through the house into the attic and cause significant damage, while fire-fighters carried out a high risk operation to achieve it.

We all understand that creating an opening remote from the fire will have the effect of moving that fire toward that opening (unless the wind blows into the opening).  Why would you remotely make an opening and create fire travel upstairs through the house while dealing with a basement fire?  Unless, of course, you have sufficient flow rate available to intervene and stop that fire spread.  This is all about the "air track" and "flow rates".

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).

Don't knock me too much on this one; like I said, I just want to understand it.  I've read the books, watched videos, even went to the USA on a study tour and received training in ventilation.  But, after all that and 25 years of fire fighting without ever cutting a h*** in the roof of a single house without any adverse impact at all, I just can't understand it.

Stay safe everyone.

Mike D

Views: 711

Reply to This

Replies to This Discussion

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

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

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

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.

Reply to Discussion

RSS

Policy Page

CONTRIBUTORS NOTE

Our contributors' posts are not vetted by the Fire Engineering technical board, and reflect the views and opinions of the individual authors. Anyone is welcome to participate.

For vetted content, please go to www.fireengineering.com/archive/.

Fire Engineering Editor in Chief Bobby Halton
We are excited to have you participate in our discussions and interactive forums. Before you begin posting, please take a moment to read our policy page. -- Bobby Halton

Be Alert for Spam
We actively monitor the community for spam, however some does slip through. Please use common sense and caution when clicking links. If you suspect you've been hit by spam, e-mail peter.prochilo@clarionevents.com.

FE Podcasts


Check out the most recent episode and schedule of
UPCOMING PODCASTS

© 2019   Created by fireeng.   Powered by

Badges  |  Report an Issue  |  Terms of Service