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In many structure fires, including the one of February 20 in which 96 people were killed, hot gasses accumulate at the top of a room until they reach "flashover" temperature (about 800-1200F), whereupon almost everything in the room ignites sending temperatures upward of 2000F.
I would propose equipping
buildings with vents that would normally be held shut by low-melting-point (200F or so) wires, but which in case of fire would pop open allowing much of the hot gas to be vented harmlessly outside.
To be sure, a hundred cubic feet of burning polyurethane foam is going to cause a problem in any structure, but if the fire gasses had somewhere to go other than through the crowds of people, it seems likely that many more people would have been able to escape.
Google 'automatic fire vent'
http://www.aecinfo....0/23/10/bilco04.htm
Well baked [Worldgineer, Oct 04 2004, last modified Oct 21 2004]
[link]
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I don't know... it'd be like a chimney, fueling the fire. |
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//I don't know... it'd be like a chimney, fueling the fire.// |
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What matters in a structure fire is how long it takes for the air in the room to reach the flashover point. There is often plenty of air in the room to reach flashover even without any ventilation. Although adding ventilation may make the fire burn more intensely by drawing more air past it, it would only do so to the extent that it was able to disperse the heat from the extra combustion. |
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That's why I'm not sure. Here it is, saving people's lives by drawing heat away, then feeding the fire and speeding it up. (head-scratching) Have to ask someone who knows. |
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I dunno. I don't think I'd like to be in the room when it reaches 200F. At this point, sprinklers should kick in. |
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Regarding the Feb. 20th fire, I doubt that this invention would have helped. From what I've heard, it was the lack of known escape routes and mass panic in the crowds that caused so many people to be trapped inside. I would speculate that many died from smoke inhalation, and then were burned by the fire. A complete lack of sprinklers didn't help, either. |
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Sprinklers are *widely* known to exist, this was a proposal for an alternative, for whatever reason sprinklers aren't there/enough, etc.. Like supercat and apparently a few other commentators, I had not known of the baked automatic fire vent's existence. I see by the link that the baked version woiks at 165° F - even at a 35° difference, as a layman, you guessed close enough for all intents and porpoises. Croissant, considering it's the thought that counts. |
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"If the building had sprinklers, we wouldn't be here right now." |
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Well, I doubt that. Sprinklers are triggered by smoke. If you've got smoke, you've got fire fighters. Those guys show up. |
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Sprinklers are almost always triggered by heat. On many, the valves are set with fusible links that melt when exposed to temperatures above 160°F or so (they range from 135°F to 575°F, depending on intended use). Others use bimetallic elements or a frangible bulb but almost all are heat activated. |
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Sprinklers are triggered by heat. A fire department visit, however, will be triggered by sprinklers. On sprinkler systems, the bleed valve often has a placard attached warning people to call the fire department before bleeding the system, to avoid having fire trucks respond. |
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The biggest killer of people in fires is smoke, that is why shopping centres, hospitals etc. have high capacity smoke spill fans which operate on the activation of a smoke/heat detector or a sprinkler system. Sure the extra air will fuel the fire, but the benefits of a smoke and heat free environment to allow safe escape of occupants and ease of firefighting operations more than outweighs the added fire intensity. Buildings nowadays have such good FRL;s that most fires will be contained to the compartment of origin, smoke however will travel easily through a building,often cause more damage to the structure internally than fire. Therefore roof vents or smoke spill fans not only allow for the safe exit of a building, but can reduce the cost to building owners and insurance companies after fire. |
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it is good to have smoke spill. Pressurised staircases also admit air to help drive smoke upwards n out through air extractor ducts n out of the building.
At what rate is the smoke spill , cft/min to be really effective?
sunlec
24 Mar2004 |
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