4 ms·

Two videos I'd like to share (well, one video, and one playlist)... The first is a 'flashover simulator'. This is a training tool for firefighters to help them

Two videos I'd like to share (well, one video, and one playlist)... The first is a 'flashover simulator'. This is a training tool for firefighters to help them recognize the signs of a 'flashover'. A flashover occurs when the radiant heat of the fire is sufficient to cause pyrolysis and ignition of more or less every surface in the room simultaneously (the floor, furniture, etc). I'm mostly sharing this because sitting in one of these is where it first clicked for me that fire burns gasses, not solids. Watching the fire snake lazily through the smoke overhead, until it felt like I was sitting on the bottom pool, looking up at the surface. https://www.youtube.com/watch?v=-Z4xxObrTlI&t=40s https://www.youtube.com/watch?v=-Z4xxObrTlI&t=40s The second is Bill Hammack (The Engineer Guy) delivering Faraday's lecture series on The Chemical History of a Candle. This is a truly excellent lecture series, despite its age (they did choose to keep most of the original language, which can take a little getting used to) https://www.youtube.com/playlist?list=PL0INsTTU1k2UCpOfRuMDR-wlvWkLan1_r https://www.youtube.com/playlist?list=PL0INsTTU1k2UCpOfRuMDR...

developer2 10y ago
That first video is visually stunning, and also gives a complete noob a good idea of what to expect from fire. It's one thing to have some generalized idea that "fire spreads quickly"; it's quite another to see how a seemingly low-key flame will almost instantly burst into an unmanageable fireball. It's interesting to see that there is a pre-emptive warning to a "flashover" - you can see the edge of the fire, for lack of better terms, "licking" or "curling" along the edge. Of course that visual warning is of little consolation if it comes with less than a couple of seconds of time to react; especially without a fire retardant suit. Imagine how many lives would be saved if every citizen could experience this kind of training first hand. I think inexperienced individuals are likely to think there is time to gather belongings "while the fire is still scaling". How many of us, upon seeing a fire "slowly" taking over a corner of the room, would believe we have plenty of time to collect our most prized or expensive possessions before running out the door? Random side thought: I wish we'd come up with a better way of testing evacuation drills. All drills do is teach people that every alarm is fake, and so everyone spends minutes packing up their laptops, grabbing their coats, etc. It's disconcerting to watch people "finishing a block of code", drinking their coffee, or texting on their phone at an office when an alarm goes off. And I've seen that at a company where the executive team planned an unannounced drill 2 months after the scheduled annual drill. As in, nobody knew it was a test. And yet it took 15 minutes to evacuate a small building. facepalm
- hvidgaard 10y ago
  The drills have their place, but I recall a place where they simply, once a month had a walk through of the procedure while doing it. Supposedly, people can actually remember it, and because there isn't any fire drills when the alarm sounds, they take it seriously.
- Symbiote 10y ago
  > 15 minutes I'll be the one leaving as soon as the alarm sounds. I've found this also sets an example and people follow. My school caught fire when I was 12, due to an electrical fault in the basement, and an adjacent building caught fire when I was about 15. University buildings I was in caught fire twice, once late in the evening and once during an exam. None of these were serious enough that we couldn't reenter the building within several hours, at least to retrieve belongings, but there'd have been no advantage to lingering inside.
- ygra 10y ago
  Flashover is visually stunning, but rare these days. Building codes should in most cases prevent it from occurring, at least in non-residential buildings (inside homes it's another matter, as there is often more combustible material than in office buildings). Even if it does happen, it requires a fire to be going on for quite a while already (pyrolysis isn't instantaneous), so everyone inside that room is either a firefighter or already dead, so I don't think training every citizen to recognise it is of much value. At work I'm one of the people responsible for evacuating employees and our only responsibility is evacuation, calling the fire department and trying to extinguish small fires (e.g. a burning waste basket, however that may happen). Anything leading to a flashover is something we should never get close to. As for the drills, you should make it clear to everyone that getting outside (or behind the nearest fireproof door) is their top priority. Hallways are going to be impassable (without passing out at least) after about three minutes, so 15 is definitely too long. I'd probably try to talk to each one of those people you're describing and make sure they understand what they're doing in that case. While they may not value their life much, their employer is on the line if they die during a fire.
- TeMPOraL 10y ago
  > Random side thought: I wish we'd come up with a better way of testing evacuation drills. A company-wide policy that if you're still inside 5 minutes after the drill starts without a good, drill-related reason (e.g. crowded stairwell), you get your performance bonus cut this month, and if you're still inside 15 minutes after the drill starts, that's ground for firing? I can't think of anything else that would make people take drills seriously. An example I remember from my high-school times that particularly annoyed me was teachers who didn't want to let the class go because they were having a test, and test is obviously more important than a fire drill...
falsedan 10y ago
> it first clicked for me that fire burns gasses, not solids I guess the materials would have some outgassing caused by the heat, but the flashover usually travels over partially-combusted particulate matter suspended in the air. Hotter fires have less smoke + soot, because they consume more of the fuel before it is carried away by convection. You can easily replicate this experimentally: light a candle, extinguish it, then light it again by applying a flame to the smoke emitted from the wick. [0] Certainly for a standard in-home fireplace fire, most of the outgassing from the fuel is actually water vapour. [0]: https://youtu.be/C5eTn5d0cvg https://youtu.be/C5eTn5d0cvg
- JshWright 10y ago
  The fire moving through the smoke is a "rollover". A flashover occurs when the temperature in a space rises rapidly, igniting most objects in the room, more or less simultaneously. A rollover is often the trigger for a flashover.
  - falsedan 10y ago
    Thanks for clarifying. I got carried away talking about smoke…
- dfischer 10y ago
  Wow – that makes a lot of sense and now I just learned an amazing trick. Thanks!
userbinator 10y ago
fire burns gasses, not solids Somewhat relatedly, the fire inside an internal combustion engine: https://www.youtube.com/watch?v=-XkL9JjHY8Q&t=195s https://www.youtube.com/watch?v=-XkL9JjHY8Q&t=195s
marcosdumay 10y ago
> fire burns gasses, not solids That depends on your definition of "burn" and "solid", really. Some fuels only turn into gas due to partial oxidation, or turn directly into plasma - paper would be a good example. Also, solids may have enough surface area to burn all by themselves - coal is a great example here.

developer2 10y ago

That first video is visually stunning, and also gives a complete noob a good idea of what to expect from fire. It's one thing to have some generalized idea that "fire spreads quickly"; it's quite another to see how a seemingly low-key flame will almost instantly burst into an unmanageable fireball. It's interesting to see that there is a pre-emptive warning to a "flashover" - you can see the edge of the fire, for lack of better terms, "licking" or "curling" along the edge. Of course that visual warning is of little consolation if it comes with less than a couple of seconds of time to react; especially without a fire retardant suit. Imagine how many lives would be saved if every citizen could experience this kind of training first hand. I think inexperienced individuals are likely to think there is time to gather belongings "while the fire is still scaling". How many of us, upon seeing a fire "slowly" taking over a corner of the room, would believe we have plenty of time to collect our most prized or expensive possessions before running out the door? Random side thought: I wish we'd come up with a better way of testing evacuation drills. All drills do is teach people that every alarm is fake, and so everyone spends minutes packing up their laptops, grabbing their coats, etc. It's disconcerting to watch people "finishing a block of code", drinking their coffee, or texting on their phone at an office when an alarm goes off. And I've seen that at a company where the executive team planned an unannounced drill 2 months after the scheduled annual drill. As in, nobody knew it was a test. And yet it took 15 minutes to evacuate a small building. facepalm

hvidgaard 10y ago
The drills have their place, but I recall a place where they simply, once a month had a walk through of the procedure while doing it. Supposedly, people can actually remember it, and because there isn't any fire drills when the alarm sounds, they take it seriously.
Symbiote 10y ago
> 15 minutes I'll be the one leaving as soon as the alarm sounds. I've found this also sets an example and people follow. My school caught fire when I was 12, due to an electrical fault in the basement, and an adjacent building caught fire when I was about 15. University buildings I was in caught fire twice, once late in the evening and once during an exam. None of these were serious enough that we couldn't reenter the building within several hours, at least to retrieve belongings, but there'd have been no advantage to lingering inside.
ygra 10y ago
Flashover is visually stunning, but rare these days. Building codes should in most cases prevent it from occurring, at least in non-residential buildings (inside homes it's another matter, as there is often more combustible material than in office buildings). Even if it does happen, it requires a fire to be going on for quite a while already (pyrolysis isn't instantaneous), so everyone inside that room is either a firefighter or already dead, so I don't think training every citizen to recognise it is of much value. At work I'm one of the people responsible for evacuating employees and our only responsibility is evacuation, calling the fire department and trying to extinguish small fires (e.g. a burning waste basket, however that may happen). Anything leading to a flashover is something we should never get close to. As for the drills, you should make it clear to everyone that getting outside (or behind the nearest fireproof door) is their top priority. Hallways are going to be impassable (without passing out at least) after about three minutes, so 15 is definitely too long. I'd probably try to talk to each one of those people you're describing and make sure they understand what they're doing in that case. While they may not value their life much, their employer is on the line if they die during a fire.
TeMPOraL 10y ago
> Random side thought: I wish we'd come up with a better way of testing evacuation drills. A company-wide policy that if you're still inside 5 minutes after the drill starts without a good, drill-related reason (e.g. crowded stairwell), you get your performance bonus cut this month, and if you're still inside 15 minutes after the drill starts, that's ground for firing? I can't think of anything else that would make people take drills seriously. An example I remember from my high-school times that particularly annoyed me was teachers who didn't want to let the class go because they were having a test, and test is obviously more important than a fire drill...

falsedan 10y ago

> it first clicked for me that fire burns gasses, not solids I guess the materials would have some outgassing caused by the heat, but the flashover usually travels over partially-combusted particulate matter suspended in the air. Hotter fires have less smoke + soot, because they consume more of the fuel before it is carried away by convection. You can easily replicate this experimentally: light a candle, extinguish it, then light it again by applying a flame to the smoke emitted from the wick. [0] Certainly for a standard in-home fireplace fire, most of the outgassing from the fuel is actually water vapour. [0]: https://youtu.be/C5eTn5d0cvg https://youtu.be/C5eTn5d0cvg

JshWright 10y ago
The fire moving through the smoke is a "rollover". A flashover occurs when the temperature in a space rises rapidly, igniting most objects in the room, more or less simultaneously. A rollover is often the trigger for a flashover.
- falsedan 10y ago
  Thanks for clarifying. I got carried away talking about smoke…
dfischer 10y ago
Wow – that makes a lot of sense and now I just learned an amazing trick. Thanks!

userbinator 10y ago

fire burns gasses, not solids Somewhat relatedly, the fire inside an internal combustion engine: https://www.youtube.com/watch?v=-XkL9JjHY8Q&t=195s https://www.youtube.com/watch?v=-XkL9JjHY8Q&t=195s

marcosdumay 10y ago

> fire burns gasses, not solids That depends on your definition of "burn" and "solid", really. Some fuels only turn into gas due to partial oxidation, or turn directly into plasma - paper would be a good example. Also, solids may have enough surface area to burn all by themselves - coal is a great example here.