# Thread: Help--Fire Doubles every minute?

1. ## Help--Fire Doubles every minute?

The rule of thumb that says a fire doubles in size every minute (some say 30 seconds)can't be found by us to reference. Does anyone know where it may be listed so that we can quote it as a reference.

2. Not 100% sure, but I think it's in the IFSTA book, but I'm not sure. I remember my training officer mentioning that too us as well, but that was last year. Sorry that I couldn't be much more help.

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Joel

If you sent us to HELL, WE'D PUT IT OUT!!

3. It took us 70 minutes to arrive on scene at a reportwed 10 acre fire, so double that every minute means it should have coverered the entire US, South America and Canada on arival. It wasn't quite that big when we got there.

Say it takes volunteers 6 minutes to get to a room and contents fire does that mean there will be 1 x 2 = 2, 2 x 2 = 4, 4 x 2 = 8, 8 x 2 =16, 16 x 2 = 32, 32 x 2 = 64 room burning in just 6 minutes?????

4. First of all LHS, thank you very much for taking the time to answer. I probably should have been more specific, I assumed most in the fire service knew the "rule of thumb" I referred to (and believe me, I know the saying about "assuming"). The fire doubling every minute (although in my basic academy 19 years ago, they told me every two minutes) has to do with an incipient stage house fire. Although the "one minute" rule is listed on many Fire Dept. web pages (some even say every 30 seconds) and is quoted by Fire Marshal's around the country, I believe the reason I cannot find literature to use as a quoteable reference (as for a report) is some of the reasons you alluded to. There are so many variables, fuel load available, oxygen depletion, type of fuel, form of fuel, etc. that no reliable text could say something as speculative as this seemingly hard and fast rule. However, that is not what a rule of thumb is. It is used just to give you a strating point or some idea as to what you may be up against in your "run of the meal" room and contents fire (if there is such a thing). By the way, What does LHS stand for (probably not the high school I attended, but it is the same). Thanks again.

5. I'm sure you have seen the NFPA video "fire countdown to disaster" it shows a small fire on a chair grow till flashover in just a few minutes. I don't remember but I thought the video made reference to fire growth. Try the fire protection handbook if you are looking for data on flame spread.

The information on fire growth is nice to know but can't be used to predict how long a member can search without a line or predict flashover. Experience will help you determine how bad a fire is, and how fast it's growing. Next live fire training you have try to get in to start the fires you can learn a great deal by just watching.

Stay Safe

6. I believe that the theory of a fire doubling in size was based on studies done by Factory Mutual Engineering and the NFPA.

I use the theory when giving fire safety talks in the schools and to other organizations. People do not realize just how fast a fire can grow from the incipient to flashover stage. If it works for us in teaching fire safety, saving lives and reducing property damage in the process, who's to argue (except for LHS*) !

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And on the eighth day...God created Firefighters!
Captain Gonzo

7. ///If it works for us in teaching fire safety, saving lives and reducing property damage in the process, who's to argue (except for LHS*) !

Cute little urban myths like the one above taken out of context by the fire service repeated over and over and without resource verification can and have been used against the fire service.

Say you're out of your station getting lunch, you miss a turn, your rig is at the union hall, having dinner at an adjoining house, you are MA to another FD, in a parade, require a 2nd tone out to fill the rig, the closest station scratches on the tone out.... then press says the 1 minute delay allowed the fire to double in size.

Or why do you need the new station, you'll still have a 3 minute run versus today's 5 minute run so the 2 minute difference will allow the fire to quadruple in size.

So what do you do when the reporter asks, "if the fire doubles in size every minute then why does the fire service literature talk about a "steady state fire". Not everyone we talk to doesn't have an education or the desire to prove us very wrong.

The press is about sensational headlines, we don't need to feed them in this world of some firefighters starting fires, committing crimes, etc. Dateline NBC, 60 minutes, etc make a living out of it. Recent press clips include: Ambulance stops at donut shop with patient in back, ambulance stops on highway with patient in back while paramedics duke it out, firefighters refuse treatment to 8 year old who later dies, Paramedic ambulance takes 28 minutes to arrive on scene and takes 1 hour 38 minutes to get to the hospital 10 minutes away on heart attack case, in only 7% of our fire deaths does the ladder arrive before the pumper so we see no reason to fix the pumps or water tanks on the quints, etc, etc.

Better use this stuff in context, lest you want it stuffed down your throat. If you want to say during the very brief incipient stage of a fire the first 2 to 3 minutes fires can double in size...that is one thing. Without spelling out the parameters you better be careful.

[This message has been edited by LHS* (edited 01-05-2001).]

8. I would hate to see anyone eat their words... but...

LHS* said "It took us 70 minutes to arrive on scene at a reported 10 acre fire, so double that every minute means it should have covered the entire US, South America and Canada on arrival. It wasn't quite that big when we got there."

Are we speaking about a wildland fire -- and how does a wildland fire compare to a compartment fire, where the radiant heat is reflected back upon the fire from the walls of the compartment - speeding pyrolysis, and lowering ignition temperatures???

You must compare apples to apples. I would have to say that there are several factors that can change the spread of a fire: Fuel load, arrangement, size of room/compartment, etc.... there are many variables that must all be taken into account - there is no answer that will fit every situation.

"Better use this stuff in context, lest you want it stuffed down your throat. ..." Sorry - but you need to heed your own advice...

9. firebartman,
I'll see if I can get you some actual references. Most of the source of this data is in research and test reports. You can search for FMRC or NIST reports. I would start with NIST. What you are basically looking at are fire growth rates. There are a couple of key fire growth rate concepts that are used fairly consistently to describe fire growth.
First, fire "size" is best characterized by its Heat Release Rate or HRR.
The basic relationship that generally defines HRR is the following: HRR = (fire intensity coefficient) x time^2. This relationship has been proven experimentally in bench test fires and very large full scale fires. With regard to time, you can see that HRR will grow exponentially over time. Let's say a fire is producing a HRR of 50 KW after 20 seconds of burning - then if you double the time to 40 seconds, the fire will be 4 times as big, if you triple the time (after 60 seconds), the fire will be 9 times as big. Fires grow fast. In fact if you look at any fire growth data for furniture, rooms, etc, the data is reported in seconds, not minutes. The fact that fires grow exponentially with time is pretty easy to show. Take any combustible surface, start a fire in the center. The fire starts to grow to form a circle. The radius of that circle is growing at a steady rate, but the size (area) of the circle is growing based on the old formula for the area of a circle A=(3.14)(r^2). So you can see how the "size" of the fire is growing exponentially.If the fire is covering a circle with a radius of 1 ft. after 10 seconds, then about 3 sq. ft of material is burning. The after 20 seconds the radius is now out to 2 ft., and the fire size is now about 12 sq. ft.(based on the area of a circle). So you've double the time and double the radius of the circle, but your area burning is 4 times as big.
The other factor is the fire intensity coefficient. There are 4 typically used, these are slow, medium, fast, ultrafast and most combustible materials fit into these types of fires. The issue with time and the size of the fire is pretty much based on the growth of the area of the circle concept. However, you can see that whether you have a material with very slow flame spread or one with very fast flame spread will impact how fast this circle keeps getting exponentially bigger. In the example I used above, if you had a material that takes 5 seconds to get from a 1 ft. to a 2 ft. radius circle, then your fire size grew 4 times bigger in 5 seconds. Then you may have a material that takes 30 seconds to get from 1 ft to 2 ft. radius and now it takes this material 30 seconds to quadruple the fire "size."
Fire growth is pretty complicated, but these general concepts can go quite a ways.

How about real fire doubling times? Reported test values are in the 10 second to 40 second range which correspond to the ultrafast down to the slow growth rates. 10 seconds though can even be slow for some materials. Ever watch a Christmas tree burn? This fire goes from ignition to 500-700KW almost instantaneously, so the fire is probably doubling every 1/10 sec or something.
In a residential type scenario, it takes about 1000KW (1 MW) fire to get to flashover. Some typical residential furniture examples are a stuffed chair-1 MW in 80 seconds/max HRR of 2 MW in 140 sec.; sofa-1 MW in 120 seconds/max HRR of 3 MW in 200 sec.
If you look on some of the residential sprinkler web sites, you will see time to flashover for residential fires in the 190-200 second which is consistent with the furniture test data. This is only a little over 3 minutes. Residential sprinklers open up about 60-70 seconds into these fires.

I'm not sure how you are using the data, but I hope this helps.
I would also suggest that you look up articles written by Rexford Wilson. I refer to his work very often. Try to find "TIME: The Yardstick of Fire Control" by Mr. Wilson. This was written in the NFPA Fireman in 1962. He comprehensively covers all of these time issues and he did so 40 years ago.

It is also very disturbing to read some of the replies to your original post. It seems some out there don't want the public to understand the realities of fire growth and the deadly effects it can have on their families so as to protect the "special interest" of the fire service. Here is a quote from Mr. Wilson's 1962 article -"we know that, realistically speaking, life safety in fires is primarily up to the occupants of the building.." Since Mr. Wilson's 1962 article, a ball park estimate is that 400,000 people have lost their lives due to fires. Fire departments, from the largest urban to the most dedicated small volunteer, could not save those people. We have also lost in the range of 5,000 firefighters during that time. In my opinion, anyone who is unwilling to tell the public the truth about fire growth and the realities of fire department response is committing a deadly fraud. I'm embarrassed and disgraced to be a firefighter when one of us is willing to trade a child's life so that we can get a new engine or station.

In the industrial sector facilities are often operated as what is called HPR or highly protected risk. Where the focus is prevention and fixed, automatic suppression and where fires, if they do occur, are put out by an extinguisher or a couple sprinkler heads. That is my vision for the fire service - one where we champion the efforts to help our communties achieve "HPR" status, and where we spend more time on prevention, inspecting and testing water supplies and automatic systems and other proactive measures, and much less on trying to get them to buy us bigger and bigger trucks.

10. FF Mcdonald

I'll try to answer any question but the original question below is what I responded to. I can't guess what someone is thinking. Key word is fire, not structure, just fire, I gave two examples. One structure one wildland. Neat little rules of thumb don't apply to either do they????

//The rule of thumb that says a fire doubles in size every minute

The above is what I responded to. If you want to change the question now knock yourself out. I'd rather not be held accountable to a question that changes after I post.

So what did I say that could possible make me eat my words?

,,Are we speaking about a wildland fire -- and how does a wildland fire compare to a compartment fire,,

Generally, I'd say wildland fires are quicker but then I've never seen more than 5000 homes burn in a day in one or kill more than 27. Our area had 10 of the 20 largest fires in the last two years none larger than Delaware. Structure fire wise I think the largest I had anything to do with killed 84 and covered 1.2 million square feet at a rate of 13 feet per second if you believe NFPA. So that is what I'm comparing with.

//"Better use this stuff in context, lest you want it stuffed down your throat. ..." Sorry - but you need to heed your own advice... //

Next time state the type of fire we are comparing.

Ok feel free to take the original question and stuff my response to the question down my throat.

Please tell me what and why?

Now do the same with my second post and finally this one.

/You must compare apples to apples.

Are we talking about fire? Or do the politicians have to? They don't have to do squat.

NEXT POINT

Fire spread is also addressed by automatic detection systems. I live in fully sprinkled home. I live in a state where all high rises old and new are fully sprinkled. No exceptions. A highrise is anything over 1 story in height.

<>

You must be talking about the fire service in general. 60% of all deaths every year there is no working detector. wanna solve the fire problem cheap and easy buy some batteries, get out and check every house and apartment.

Need someone to copy try Granbury Texas (I know they are volunteer) they do every home and give everything away. There you go 2400 lives. That leaves a whopping total you can do anything about to the tune of less than 20 deaths a state. How much you want to spend to fix it? It cost our state 1/2 billion to get rid of the highrise public occupancy problem. Remember, that 4000 figure includes plane crashes and motor vehicle fires.

Education might have a value but it is hard to measure in a country where USFA shows some states have a 11 to 38 times higher chance of death to fire than others. Even whenthey share a common boarder. Better code states win. No code poor code states always lose.

//Mr. Wilson's

Would support the above.

//1962 article -"we know that, realistically speaking, life safety in fires is primarily up to the occupants of the building.."

That's not true if the state or government makes them sprinkle the place, it has been handled for them. NEVER EVER has a person died in a sprinkled home.

/// Fire departments, from the largest urban to the most dedicated small volunteer, could not save those people.

Not via suppression after the fact. Sprinklers and notification sure would. John Hopkins did a study in 1979 that said sprinklers and smoke detectors would have a 98% success rate in stopping fire deaths.

However, the requirements for residential sprinkler systems that by code cannot be hooked to a majority of the domestic drinking water systems in the US has insured domestic sprinklers will never take off. High cost is another.

I think this Old House Magazine had it right, when they suggested partial sprinklers in the areas of the home that have the highest fire starts. The heater/hot water heater room and the kitchen. Right there is over 50% of the fire starts. The investment on an old or new home is \$100 to \$400. I think it would be an excellent start, the road we are on is not working.

///We have also lost in the range of 5,000 firefighters during that time.

50% of those died of heart attacks, are you sure that number was preventable not having fires? Or is the primary cause of those deaths being male and life style?

//In my opinion, anyone who is unwilling to tell the public the truth about fire growth and the realities of fire department response is committing a deadly fraud.

Telling them it doubles every minute is a fraud. Did you notice during the Riots of the 60' and 90's the cities did not burn down. Good building codes is why. Almost all interior structure fires become oxygen limited which stops the tremendous growth in the incipient state and establishes the steady state fire.

I find interesting and here is a book on the subject that says if you have fire trucks spaced every so often around the city you can insure flashover will not occur. In fact It is being used to sell city councils.

The reality of fire department response is most people according to NFPA are dead

in minutes
40 plus 38%
20 to 40 20%
10 to 20 18%
5 to 10 9
0 to 5 15%

before we are notified so the investment should be in notification systems, flame retardant fabrics, self extinguishing cigarettes and automatic suppression systems. Note most can be regulated by the state.

//much less on trying to get them to buy us bigger and bigger trucks.

If you go back as far as you like, you will find, the largest loss structure fires in the US each year are fully sprinkled buildings (not always working or designed for the risk). So there is still work to be done there.

I'm sure we'd be embarised to se a show of hads of how many firefighters live in sprinkled housing.

Oh, Day Two no source for the doubling every minute!!!

11. I believe what they're trying to say is that fire doubles in "intensity" every minute, not necessarily "size".

12. Whoever finds the reference to this little "rule of thumb, please let us know so we can let the author know that it is total unadulterated nonsense.

Anyone who has studied fire science learns about a word called "variable". Do you realize that fire is a 100% predictable mathematically calculable phenomenon that, given the same set of circumstances, will do the exact same thing every time?

What's that? No two fires EVER burn the same? EXACTLY! Because of variables. Here's a small list of the variables that must be considered when calculating burn rate in a compartment fire.

Material burning (form and amount)
Ventilation
Humidity
Room size
Room openings (number, size and height)
Wall materials
Ceiling Height
Ceiling material
Floor material
Time
Fire suppression systems
Fire department intervention

A room fire involving a couch with an open door and two windows, in a room with sheetrock walls and seven foot ceilings will develop much faster than the same fire in the same room with an eight foot ceiling.

Do yourself a favor. Learn this job, really learn it. And throw the shortcuts and "rules of thumb" out the window. They are dangerous.

13. LHS* --

I'll stick to my original posting.

I apologize for trying to pick you apart - I fell prey to you. I did just what you do, to everyone - Pick them apart- and try and tell them they're stupid, or wrong.

Oh well.....

See everyone in the Forums.....

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Marc

"In Omnia Paratus"

-- The opinions presented here are my own; and are not those of any organization that I belong to, or work for.

14. Thanks to everyone who responded, particularly those that attempted to help. "ffeng", you deserve a special thanks as your info was probably the most helpful. The reason for the inquiry is my dept. is in the process of relocating a station. We feel it should go one direction and some "city fathers" feel it should go another. By using fire loss history for the district, I am attempting to predict future fire loss based on increased or decreased reponse times to the majority of our fires. To do this I had to use "some" factor, as we would ALL AGREE that fire damage will increase as the time a fire goes unchecked increases. As you move your starting point around you get closer to some fires and farther from some. But since the location we are recommending is closer to the majority of our fires, our location choice will reduce the fire overall fire loss. I was hoping to find a source I could reference that said a generally accepted (broad) rule of thumb is "fire doubles every ?". I still havn't really found that reference. But thanks anyway to all who responded--Anyone else have that reference for me?

15. >>I was hoping to find a source I could reference that said a generally accepted (broad) rule of thumb is "fire doubles every ?". I still havn't really found that reference. But thanks anyway to all who responded--Anyone else have that reference for me?<<

It doesn't exist. That's what people were trying to tell you.

George

16. I've seen the reference, it's in the same book that says if you don't put a structure fire out with the first 250 gallons it's going to the ground...

17. Firebartman: I appreciate the fact that your looking for a source of the ongoing quote of fire doubling in size every ..?..seconds.

Confident that it was not directly written anywere I chose not to look any further for the answer to your question.....until reading numerous responses!

I think the best source of information relating to your question can be found on page 1-27 and 1-28 of the 17th Edition of the NFPA Fire Protection Handbook. This probably provides the clearest explanation why there is not a single number that could apply.

What I found the most interesting in that section was the discusion relating to fire growth to the ceiling.

"Different rooms pose different levels of risk regarding the likelihood of reaching full room involvement and the time in which fire development takes place. The factors in Table 1-2B provide a general guide to the important types of factors. If one were to focus on a single event that might be used to represent the relative level of risk posed by the contents and interior finish in a room, it would be the ability of flames to reach the ceiling. The arrangement of contents and types of fuels where it would be difficult for fire to grow to touch the ceiling pose a relatively low fire growth hazard potential. On the other hand, where funiture conbustibility and density will allow a fire to develop to ceiling height, or when combustible interior finish is present, the fire growth hazard potential usually is comparatively high."

Again, the above quote is from the NFPA 17th Edition of the Fire Protection Handbook.

Although it still does not provide you with a source to the quote you mention, I do hope the info helps.

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Kirk Allen
First Strike Technologies, Inc

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