1. #1
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    Default Backdraft or Smoke Explosion

    Hello Brothers...

    I read with great interest the photostory on the front page of Firehouse.com this morning. It is the one where several brothers in PA narrowly escaped inury from a Backdraft explosion. I'm starting this thread because it appears from the pictures and from what everyone was doing that "everything was being done correctly." I can't say that I would've done anything different...however, I have a couple of questions. This is not a critique...I'm trying to learn from these guys so that nobody on my crew gets hurt.

    http://cms.firehouse.com/content/art...Id=45&id=50000

    First of all...was the explosion a true backdraft, or was it a "smoke explosion," where the smoke fell within it's explosive ranges down in the basement? How do we keep ourselves from getting into the same position? Would it have helped to ventilate more prior to the first hoseline entering? From the description, it seemed like it would have appeared to be a fire on the second floor? What other size-up cues can be looked for?

    Again...this is not a critique. It is intended to figure things out from a size-up and tactics point of view to prevent injuries and deaths.

    Stay safe, everyone.

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    I am with you brother, other than ventilating more I am not sure what else could have been done. Even then I am not sure the extra ventilation would have helped because the basement was what needed to be vented and there apparently was no evidence of fire in the basement from the size up. Maybe better recognition of building construction. Taking note that this appears to be a ballon frame house, sending someone to the basement to check might have helped, if there was time before the explosion. Although I wasn't there, I too would venture a guess and say that maybe it was a smoke explosion instead of a backdraft. I say this because from my limited knowledge the smoke appears to be dark black, not that dirty brown smoke that is said to come before a backdraft. Those are my 2 pennies worth. I would love to hear from some more.

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    Do you have any source material that actually says there is a difference between a backdraft and a smoke explosion? Because I am confused what the difference in your scenario is. PLease provide a citation for a scientific basis for this distinction.

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    I am a bit confussed on the "Basement Flashed then backdraft" comment in the story.....

    A misunderstanding on these phenomenon are common. Flashovers are often mistaken with backdrafts because of the pressure release when EE windows give, and the windows in the picture look to be EEWs. And again...these pictures look to me like a flashover occured. It seems that the fire was breathing ok.....and to go from free burn to smolder in about a minute then with backdraft conditions....I don't know....To me...by whats written, it sounds like a violent flashover.....

    But....as far as backdrafts go....if conditions are present....then a-lot of good venting must be done prior to entry....all that pressure has to be released carfully. If that means cutting a hole in the first floor....then do so. In basements of ballon frames, you could....find a window as close to above the fire you can get, stretch a line to that point (most likey the 2d line, first protects the interior stairsm 3d could make the push into the basement, exposes the bays in the wall...., open the window, cut the hole about 1 foot from a window....and vent.....just don't operate the line into the hole....you could use it the knock back flames that are impeading....or you could drop a celler distributor into the hole and knock it down....I have done both with success.
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    The pictures and the story don't appear to match. Is the third pic from the bottom after the "backdraft"? One of the windows appears to be completely intact. Is the picture below it the front door? The storm door looks remarkably intact for the door behind it to have been blown off it's hinges. This series of photos looks like a fire in a balloon frame with a flashover,and some extension to an exposure. Are they the right ones? It's not very likely that a balloon frame would be tight enough to produce a backdraft, is it?

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    "Less than one minute after the basement flashed a backdraft occurred."

    This statement by itself is inconsistant with a backdraft. If in fact, there we backdraft conditions in the basement before the reported backdraft occurred, a flashover could not have occured as a true backdraft condition requires an enviroment with an oxygen deficienancy and a flashover condition requires an oxygen rich enviroment.

    This simply sounds like either a rapid expansion of fire gowth or a mini-explosion fuled by some highly combustable material stored in the basement.

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    They also say that the two firefighters were in the dining room when it flashed, yet they crawled out after the fire rolled over them. That itself is inconsistent with a flashover.

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    Quote Originally Posted by GTRider245
    They also say that the two firefighters were in the dining room when it flashed, yet they crawled out after the fire rolled over them. That itself is inconsistent with a flashover.

    Well, it says one guy was at the door of the dining room, the other was 3 feet in, so it sounds like the room flashed over, or, more likely, the basement flashed over and pushed some heat and smoke on to the floor above . Doesn't sound like a backdraft, though.

    So those are the correct pictures?

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    Default Backdraft or Smoke Explosion Reply to Thread

    Vincent Dunn has documented the difference; Check on his web site I believe he has it posted their.

    Vesrescue

    http://vincentdunn.com/dunn/newsletters/dec/dec.pdf
    Last edited by vesrescue; 07-02-2006 at 02:07 PM.

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    Question Me Too.

    I also was a little confused when I saw this article. I think the pics are correct, and maybe that's just how crazy things actually got. Not sure as to what it may have been, but there was definitely a significant event, and I'm glad they made it out. With all that fire, though, I don't think backdraft is the right word.

    We had a similar one in a 2-story house, started in the 1st floor ceiling, extended to the 2nd floor, got into a pipe chase with PVC piping and burned DOWN to the basement. Doesn't always go up. No smoke showing from the basement when we arrived either, just like the photos with the article. Next thing we know, fire is poking up through the 1st floor FLOOR!

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    Quote Originally Posted by clancyxdogg
    Well, it says one guy was at the door of the dining room, the other was 3 feet in, so it sounds like the room flashed over, or, more likely, the basement flashed over and pushed some heat and smoke on to the floor above . Doesn't sound like a backdraft, though.

    So those are the correct pictures?
    It says nothing about that firefighter who was three feet in the door being on fire either, therefor one of two things happend. Either the report is incorrect, and that firefighter did infact catch on fire, in which case a flashover may have happened, or they didnt expirience a flashover. More than likely, the basement may have flashed and therefor caused a ROLLOVER in the dining room.

    What many people fail to realize is that if you say you have survived a flashover, yet you have never been on fire, you didnt survive a flashover.

    I am agreeing with whoever said that there may have been an explosive substance of some sort in the basement that caused that exposion, becuase so far it isnt meeting the characteristics of any of the mentioned fire behavior stages, such as backdraft or flashover. The only one I can see that may have happened is a rollover caused by some type of accelerated explosion.

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    Quote Originally Posted by vesrescue
    Vincent Dunn has documented the difference; Check on his web site I believe he has it posted their.

    Vesrescue

    http://vincentdunn.com/dunn/newsletters/dec/dec.pdf
    You're right. He documented it. From Page 1:

    "A backdraft is a smoke explosion."

    If we take Chief Dunn's word for it, as I am easily led to do, then it is proof tha tthis thread was started by someone with, how can I say it.....NO KNOWLEDGE of fire science trying to sound intelligent.

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    Quote Originally Posted by phyrngn
    Again...this is not a critique. It is intended to figure things out from a size-up and tactics point of view to prevent injuries and deaths.

    Stay safe, everyone.
    That deffinatly does not sound like the situation you just described.

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    Quote Originally Posted by GeorgeWendtCFI
    Do you have any source material that actually says there is a difference between a backdraft and a smoke explosion? Because I am confused what the difference in your scenario is. PLease provide a citation for a scientific basis for this distinction.

    I prefer to make a distinction between backdraft and smoke explosion. I realize that many sources consider these to phenomenon identical, but some do not. See “Enclosure Fire Dynamics” by Karlsson and Quintiere (2000, CRC Press) pages 16-17.

    The difference is that a backdraft occurs in the fire room. A smoke explosion occurs in a room adjacent to the fire room (above, below, or to the side). Smoke (including flammable gases such as CO, unburned hydrocarbons, and pyrolyzates) escape from the fire room and migrate to an adjacent room where ignition occurs resulting in a smoke explosion.

    I believe (IIRC), the principle contributor to the backdraft or smoke explosion is not CO, but the unburned hydrocarbons. CO may not even reach its LFL (LEL).

    The ignition dynamics of a backdraft and a smoke explosion are decidedly different. Hence, the need for two definitions.

    I don’t know who the “Keeper of the Official Fire Definitions” is, but if it is decided to equate backdraft with smoke explosion, then a new definition is needed for what I call a smoke explosion.

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    Quote Originally Posted by FireH2O
    I prefer to make a distinction between backdraft and smoke explosion. I realize that many sources consider these to phenomenon identical, but some do not. See “Enclosure Fire Dynamics” by Karlsson and Quintiere (2000, CRC Press) pages 16-17.

    The difference is that a backdraft occurs in the fire room. A smoke explosion occurs in a room adjacent to the fire room (above, below, or to the side). Smoke (including flammable gases such as CO, unburned hydrocarbons, and pyrolyzates) escape from the fire room and migrate to an adjacent room where ignition occurs resulting in a smoke explosion.

    I believe (IIRC), the principle contributor to the backdraft or smoke explosion is not CO, but the unburned hydrocarbons. CO may not even reach its LFL (LEL).

    The ignition dynamics of a backdraft and a smoke explosion are decidedly different. Hence, the need for two definitions.

    I don’t know who the “Keeper of the Official Fire Definitions” is, but if it is decided to equate backdraft with smoke explosion, then a new definition is needed for what I call a smoke explosion.
    I think you may be taking that Karllson definition out of context a little. If not, he is alone on this one. Even Quintere's other works don't support that definition.

    I also do not agree that there is a "decidedly different" ignition dynamic in the two scenarios you discuss. Both siutations involve under ventilated compartments filled with heat and products of combustion. Both involve piloted ignition. Both involve a deflagration. Both involve potentially catastrophic pressure increases. The only difference is in the semantics of where the event occurs. You seem to want to limit the location of a backdraft to the fire room. A smoke explosion in any other location, using your definition, must be differentiated from a backdraft. The defies logic.

    I have investigated incidents involving backdrafts. I have seen little to no difference in the pre-event or post-event data.

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    Default Just my 2¢...

    Hi,

    The way I've always seen it is that backdraft occur when oxygen is added to a previously oxygen starving fire. And, a smoke explosion will occur when the right fuel/oxygen mix meets with an ignition source.

    I've alway understood that both conditions are missing an ingredient;

    Backdraft = Oxygen

    Smoke explosion = heat source

    But, anyway, just vent the f!"/$% room!!!

    Regards,

    Sly

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    Quote Originally Posted by GeorgeWendtCFI
    I think you may be taking that Karllson definition out of context a little. If not, he is alone on this one. Even Quintere's other works don't support that definition.

    I also do not agree that there is a "decidedly different" ignition dynamic in the two scenarios you discuss. Both siutations involve under ventilated compartments filled with heat and products of combustion. Both involve piloted ignition. Both involve a deflagration. Both involve potentially catastrophic pressure increases. The only difference is in the semantics of where the event occurs. You seem to want to limit the location of a backdraft to the fire room. A smoke explosion in any other location, using your definition, must be differentiated from a backdraft. The defies logic.

    I have investigated incidents involving backdrafts. I have seen little to no difference in the pre-event or post-event data.
    The difference between a backdraft and a smoke explosion is that a backdraft occurs after the introduction of oxygen,a smoke explosion is a situation where smoke and sufficient oxygen are present but the mixture is below it's ignition temperature.The explosion occurs due to the introduction
    of a flame or spark.

    Don

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    Quote Originally Posted by don120
    The difference between a backdraft and a smoke explosion is that a backdraft occurs after the introduction of oxygen,a smoke explosion is a situation where smoke and sufficient oxygen are present but the mixture is below it's ignition temperature.The explosion occurs due to the introduction
    of a flame or spark.

    Don
    That is a FF1 explanation of a backdraft. It is far more complex than that.

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    George,

    Did you wake up on the wrong side of the bed today?

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    Quote Originally Posted by WebFire
    George,

    Did you wake up on the wrong side of the bed today?
    I don't know what you are talking about.

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    Default Thank you

    Thank you to all who have posted in a positive manner. If you read any of my posts, they are typically positive and do not offer a critique. The reason that I post on this forum is to learn, because I (unlike George) do NOT know it all. If I am confused about something, I ask. If I've read something somewhere, and I see something different somewhere else, I ask. No I do not have a lot of fire experience. I am in a part of the country that, by the nature of the business, could find myself in a leadership position. This is something that I take to heart, and do not EVER want to walk to the front steps to tell a widow that her beloved firefighter passed because of something I didn't know or didn't know about. The thread was never started with the intent to critique or belittle anyone for any department. If we put ourselves on the internet and turn in pictures for stories, that is a chance we take. I'm only trying to glean from the experiences of others in order to perfect my size-up skills so that no one on my watch is injured or killed.

    George, if you feel that I was trying to make myself look intelligent by posting this, then I am sorry for you. I have always had great respect for your knowledge and what you had to post, and your condescending remarks did, in fact, jab at me a little. Perhaps if you knew me and my passion for the fire service, you would know that I'm just trying to get things right. But, I've been in this line of work long enough to have thick skin, and know that it's easy to hide behind our "internet personas," so I'll just take it.

    I am glad to see that my thread has at least spawned some good discussion (for the most part), and hope that at least my correct spelling shows some signs of "intelligence."

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    Quote Originally Posted by phyrngn
    Thank you to all who have posted in a positive manner. If you read any of my posts, they are typically positive and do not offer a critique. The reason that I post on this forum is to learn, because I (unlike George) do NOT know it all. If I am confused about something, I ask. If I've read something somewhere, and I see something different somewhere else, I ask. No I do not have a lot of fire experience. I am in a part of the country that, by the nature of the business, could find myself in a leadership position. This is something that I take to heart, and do not EVER want to walk to the front steps to tell a widow that her beloved firefighter passed because of something I didn't know or didn't know about. The thread was never started with the intent to critique or belittle anyone for any department. If we put ourselves on the internet and turn in pictures for stories, that is a chance we take. I'm only trying to glean from the experiences of others in order to perfect my size-up skills so that no one on my watch is injured or killed.

    George, if you feel that I was trying to make myself look intelligent by posting this, then I am sorry for you. I have always had great respect for your knowledge and what you had to post, and your condescending remarks did, in fact, jab at me a little. Perhaps if you knew me and my passion for the fire service, you would know that I'm just trying to get things right. But, I've been in this line of work long enough to have thick skin, and know that it's easy to hide behind our "internet personas," so I'll just take it.

    I am glad to see that my thread has at least spawned some good discussion (for the most part), and hope that at least my correct spelling shows some signs of "intelligence."
    Boo-hoo.

    I do not know it all. But I know about this.

    If you think that was condescending, you need a much thicker skin, buddy.

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    George, perhaps when Paul Grimwood sees this thread he'll post his thoughts on a backdraft vs. smoke explosion, and you can then argue with him.

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    Default Backdraft and Smoke Explosion

    Sorry for my late entry into the discussion but I have been on the road.

    First to address the issue of definitions, there are a number of different definitions for fire behavior phenomena. However, I would agree that Karlsson and Quintiere provide a good starting point.

    Flashover: The transition from a fire in the growth state to fully developed stage. Adequate oxygen is required for this to occur (either as part of initial development in the compartment or subsequent to increased ventilation)

    Backdraft: Ignition of flammable products of combustion and unburned pyrolysis products from a underventilated fire. This may occur as autoignition or piloted ignition. However, conditions for a backdraft typically involve high temperature and limited air supply prior to occurance.

    Smoke Explosion: Piloted ignition of flammable products of combustion or pyrolysis products that are premixed with air and within their flammable range (not a common event).

    For a more detailed discussion and case studies, see my series of articles on extreme fire behavior on this web site.

    The difference between a ventilation induced flashover (flashover following an increase in ventilation when the fire is ventilation controlled) and backdraft is the rate of increase in energy release (backdraft generally has a more rapid increase in heat release rate and subsequently is often more violent, particularly when confined). However, a vent induced flashover is also quick and can result in a considerable "push" of hot gases. It is difficult to differentiate between these phenomena on the fireground (and it may not be that important as the initating factor and mitigation tactics are essentially the same).

    Looking at the photos in this incident, I would guess (based on the limited information available) that this was in the what the Swedes would call the "gray area" between vent induced flashover and backdraft. In either case, cooling the gases (i.e. indirect attack) and ventilation (a bit tougher given the fire location) provide two tactics to mitigate the hazards presented.

    The first photos do not show smoke from the basement, but smoke, air track, and heat indicators may have been visible on closer examination (limited smoke under pressure, stained and/or cracked windows, air track into the basement, etc.). It is always difficult to read the fire from a still photo, but looking for critical cues provides good practice and a starting point for discussion.
    Ed Hartin, MS, EFO, MIFireE

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    Thank you, Mr. Hartin for your explanation. And thank you for maintaining the spirit of this thread, which is to learn. Your answers are extremely helpful.

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