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stuckupmyownera
11-09-2010, 04:34 PM
It's an old English stone farmhouse. A petrol soaked burning rag gets dropped through the letter box.

I'm thinking the curtains over the door would go up first, maybe catch some coats on hooks and some furniture nearby. But how long before the fabric of the house starts to burn (floors, ceilings, wallcoverings)? How long before it reaches the next storey?

I'd be grateful for any info anyone can give.

milly
11-09-2010, 04:41 PM
a lot of this depends on how quickly the vapors of the petrol burn too...i'd research flash points, burn rates, etc to make sure you get this right...for example, I've seen people start fires with kerosene vs. gasoline to make it a slow burn as opposed to an explosion...

and if the fire was set inside the house, ie, the setup was done there, the place would go quicker because of the burning vapors is what I'm saying...otherwise, I think it really depends on what is in the room when the rag is dropped in...also, fires need oxygen, so you'd probably want to drop the rag into an area with some openings...that would help it to grow and spread quickly

:)

if you'd like to know more, feel free to PM me...

thothguard51
11-09-2010, 04:55 PM
Here is a secondary question...

Does how the fire spreads matter to the story line? If no one is observing the fire, then it will not matter how the fire spreads. If someone is observing the fire, are they feeding it or trying to put it out?

If you need this information for say an investigator, they I do strongly suggest researching chemical and fire properties as Milly suggested.

All in all, I would say the spread will depend on how the immediate area is constructed, what it is constructed of, and any flammable clutter in the immediate area to feed the flames once they start.

jclarkdawe
11-09-2010, 06:08 PM
It's an old English stone farmhouse. A petrol soaked burning rag gets dropped through the letter box.

I'm thinking the curtains over the door would go up first, maybe catch some coats on hooks and some furniture nearby. But how long before the fabric of the house starts to burn (floors, ceilings, wallcoverings)? How long before it reaches the next storey?

I'd be grateful for any info anyone can give.

First thing is your version sounds plausible. Second thing is that my vision of an English stone farmhouse is a structure in which the exterior walls are stone, interior walls are wood or plaster, the roof is wood and asphalt shingles, and there are minimal piercings for windows.

The fire triangle consists of three aspects: fuel, heat, and oxygen. A fire needs all three in sufficient quantities to work. Let's start with the fuel. England and the United States are very aggressive about reducing flammability of items. There's a video comparing a Danish sofa and an English one on the internet somewhere. The English one never gets burning very well. So depending upon the age of the material, objects like furniture, clothing, and bedding may have a significant amount of flame retardant in it.

Modern walling material is relatively resistant to fire compared to the older lathe and plaster style. Wood paneling burns the best, but the farther the wood paneling is from being pure wood, the less well it burns. A stone floor doesn't burn at all, nor will tile.

So the initial question is how much material is in each room (the more cluttered the more things to burn) and what are those materials. A modern office building might only have for fuel sources paper and plastic and the rest of the material might never burn, including the walls. An old Victorian house would have a substantial fire load, and burn very well.

Second element is heat. As the heat in the fire area builds, more and more stuff becomes flammable. Heat is a function of the area that needs to be heated, being easier in a small room compared to a larger. And heat is vertically structured. The area closest to the floor will be the coolest (maybe 100 degrees F.) while the ceiling might be 800 degrees F. Heat will actually form layers in the room as the fire builds. This is one of the reasons that fire climbs well but doesn't descend very well. In other words, a fire that starts in the basement will take out a house better than a fire that starts in the attic.

Last element is oxygen and in a stone structure, this is a big one. A fire needs a lot of oxygen, which flows from the fire pushing hot air up (smoke) creating a vacuum situation at the base of the fire. Oxygen rushes in to fill this vacuum. In brush fires, this situation can create winds that are over 30 mph (50 kph) strong.

As a fire burns, it sucks up all the oxygen in a room, until it runs low, at which point the fire will begin to smolder, generating a lot of heat, but not burning very efficiently. Eventually, it will starve itself of oxygen and go out if no more oxygen can get to it. Obviously this happens faster in a small room than a large room and is why a barn fire takes out the whole building so quickly.

Walls, doors, and windows will prevent oxygen from getting into a room up to their fire rating. For instance, more fire doors can survive a lot of fire before failure. Walls are more likely to last than doors and windows, so typically you look at the piercings. Windows will at a certain temperature blow out, and doors eventually catch fire, depending upon their construction. Hollow core doors are the most flammable.

Once the windows/doors go, the fire has unfettered access to oxygen and will burn well. Until the windows/doors go, it will be a smoldering, smokey, hot mess. And because of the heat buildup before the windows/doors go, when they do go, you'll get a flashover as the oxygen suddenly enters this super-heated area.

Short answer is without knowing all of this, there's no way of predicting how a house will burn. A simple thing like whether you keep interior doors shut makes a significant factor. There are probably quite a bit of video of fires on the internet. Watch them and see how things burn.

I was formerly a captain on the local volunteer fire department.

Best of luck,

Jim Clark-Dawe

stuckupmyownera
11-09-2010, 08:45 PM
Thanks everyone so far.

After the fire's been burning just a couple of minutes, someone breaks a window in the same room and climbs in to try to put it out (although he soon gets distracted by bigger problems). So I'm thinking there'll be no shortage of oxygen.

Like I said, it's an old building. I'd suspect the interior walls and ceilings were original - all wooden beams and plaster - though the plaster will have been painted more recently.

Is it reasonable to have the ceiling catch fire above the curtains fairly quickly?

And once the ceiling's on fire, how is it likely to spread? Horizontally? Or will it eat up into the space under the first-floor floorboards (not a lot of oxygen there I guess) and start to spread upstairs?

I don't know how much detail I can give. It's a fairly big living/dining room. Neither very bare nor very cluttered. A mix of old and new, bought and homemade. I can easily tweak some of the details to make the fire work if I need to :)

Kenn
11-09-2010, 10:54 PM
The horizontal spread of fire is usually via the radiation of heat from hot smoke. This can cause combustible vapours to be given off, or furnishings, etc. can simply ignite. If you Google flashover, there are bound to be some examples of this (but beware, this is different to flashback).

There was a TV programme about homes from hell where a house was gutted by fire. I caught the tail end of it a week or so ago. I think it is being shown this Saturday at 2000 on ITV2. Maybe worth a look.

jclarkdawe
11-09-2010, 11:21 PM
Thanks everyone so far.

After the fire's been burning just a couple of minutes, someone breaks a window in the same room and climbs in to try to put it out (although he soon gets distracted by bigger problems). So I'm thinking there'll be no shortage of oxygen. No, but there might be a shortage of the person. He's likely to become a crispy critter. If there is no open door in the room, the room will quickly heat up, creating a high pressure zone. When the window is broken, the heat and flames will shoot out the window, briefly creating an extremely high temperature area in front of the window (if you've seen the movie BACKDRAFT, you've seen this effect). A person standing in front of the window will be blown away by this effect, but not before being burned severely. A firefighter, in taking out a window, will do it from the side of the window, standing against the wall, reaching over with an ax to break the window, keeping as low to the ground as possible. First time you do this, it will scare the shit out of you.

What will then happen is the smoke will start going out the top of the window while oxygen will start flowing in the bottom. Flames will immediately start burning a brighter orange (dull orange is an indication that a fire is starved for oxygen). Heat will actually drop as the heat is vented with the smoke, and the room will clear substantially of smoke (this is why firefighters break the windows and put a hole in the roof).

Oxygen starvation for a fire happens very quickly. Assuming an average size house, a fire can consume enough oxygen within a couple of minutes to be in starvation mode. At this point, the house starts to fill with smoke with a smoldering fire. Not only will the window breaking cause the fire to shot out the window, the fire will also scorch the entire interior that is not blocked by doors. This fire will burn very quickly, but at a high temperature. Some items will catch fire, while others will not, and this fire will die down within seconds.

Opening the door or breaking the window of a burning house can be deadly.

Like I said, it's an old building. I'd suspect the interior walls and ceilings were original - all wooden beams and plaster - though the plaster will have been painted more recently. I'm not sure, as we don't have many stone buildings in the US, but I think the interior side of the exterior walls have the plaster fastened directly to the stone, which means those walls have no flammable material. It takes quite a lot of heat and fire before the interior walls start dropping their plaster so that the lathe work is exposed and starts burning. Once it gets into the walls, however, it spreads very rapidly. Big beams can be hard to burn because of their size.

Is it reasonable to have the ceiling catch fire above the curtains fairly quickly? If the ceiling was wood beams under a wood floor for the second story, possibly. If the ceiling is plaster, probably not. Ceilings don't burn that well. Usually the furniture is going to be burning before the ceiling goes. But the material here makes a lot of difference. And a ceiling where some of the plaster has dropped off can be very flammable.

And once the ceiling's on fire, how is it likely to spread? Horizontally? Or will it eat up into the space under the first-floor floorboards (not a lot of oxygen there I guess) and start to spread upstairs? It will spread both horizontally and vertically. It will also start getting into the walls. (Walls and floors are actually rather hollow between the studs/beams and fire travels very well through them. One thing to understand in fires is that the heated air will contain incompletely burned particles. These will float around in any heated area, until suddenly enough oxygen enters the area. Then the burst into flame, making it look like the air is burning. But this heated air will travel throughout the structure once it gets into the walls.

I don't know how much detail I can give. It's a fairly big living/dining room. Neither very bare nor very cluttered. A mix of old and new, bought and homemade. I can easily tweak some of the details to make the fire work if I need to :)

Some videos for you to look at are Room Flashover Videos.mpg, (http://www.youtube.com/watch?v=QqMVm72FMRk)Backdraft/Smoke Explosion, (http://www.youtube.com/watch?v=aTQWNCeCBvQ&feature=related)flashover (http://www.youtube.com/watch?v=ct5YIkM9nMc&feature=related)

Best of luck,

Jim Clark-Dawe

stuckupmyownera
11-10-2010, 12:27 AM
Wow, thanks so much for this, Jim. I didn't know it could happen so fast!

And thanks for the heads-up on the programme, Kenn.

Tsu Dho Nimh
11-10-2010, 01:50 AM
It's an old English stone farmhouse. A petrol soaked burning rag gets dropped through the letter box.

I'm thinking the curtains over the door would go up first, maybe catch some coats on hooks and some furniture nearby. But how long before the fabric of the house starts to burn (floors, ceilings, wallcoverings)? How long before it reaches the next storey?

What does the plot need? Tell us that and we can tell you what the house has to be like inside for it to happen.

A petrol-soaked rag isn't going to have Molotov cocktail-like properties. It's more likely to burn the one doing the dropping through the letterbox. It won't explode because it's already burning