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Post by ironhold on Oct 19, 2015 14:16:10 GMT
Had a bit of an odd dream last night.
In it, I was essentially living a spy movie. A VIP was hiding out in a three bed, two bath house in suburbia. I was part of a team assigned to keep him safe.
It turned out that someone in the group responsible for the mission was one of the bad guys. To this end, they had arranged a trap. A pair of CO2 fire extinguishers had been modified so that they would discharge when given a remote signal to do so. They were then placed inside the house's ventilation system.
The idea was that when the extinguishers discharged, the CO2 would flood the house, suffocating everyone who was inside.
But would such a trap even work in real life?
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Post by the light works on Oct 19, 2015 14:37:45 GMT
Had a bit of an odd dream last night. In it, I was essentially living a spy movie. A VIP was hiding out in a three bed, two bath house in suburbia. I was part of a team assigned to keep him safe. It turned out that someone in the group responsible for the mission was one of the bad guys. To this end, they had arranged a trap. A pair of CO2 fire extinguishers had been modified so that they would discharge when given a remote signal to do so. They were then placed inside the house's ventilation system. The idea was that when the extinguishers discharged, the CO2 would flood the house, suffocating everyone who was inside. But would such a trap even work in real life? They would have to be pretty massive to displace enough oxygen to do serious harm. keep in mind they are commonly used to extinguish stuntmen doing fire effects.  that said, an oxygen displacement strategy could theoretically be deployed. I understand unconsciousness from lack of oxygen is pretty quick, with little to no warning signs. |
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Post by GTCGreg on Oct 19, 2015 16:00:28 GMT
I believe this was one of the problems with the halon fire suppression systems used in computer rooms. They suffocated the fire, but also anyone else who happen to get trapped in the room.
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Post by the light works on Oct 19, 2015 16:11:06 GMT
I believe this was one of the problems with the halon fire suppression systems used in computer rooms. They suffocated the fire, but also anyone else who happen to get trapped in the room. right. in the telephone relay station I did some work in, there was a delay and a manual panic button, so in the event of a false alarm you could hit the panic button and prevent discharge - otherwise, it is a case of running for the door. our standing order for the cable company's modem room is if the outside alarms are going off, assume there is nobody inside to rescue - they are either out or dead from oxygen displacement. (also there is nothing in there we can put out with water) |
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Post by wvengineer on Oct 19, 2015 23:39:47 GMT
I did an equipment installation in an anacohic chamber (sound, light, & RF shielded chamber) and they installed an FM200 based fire suppression system in there. Supposedly, it is safe to use in populated areas, unlike Halon. My question there is how does it work? If it doesn't freeze the area or displace the o2 content, how does it put out a fire?
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Post by the light works on Oct 20, 2015 4:20:23 GMT
I did an equipment installation in an anacohic chamber (sound, light, & RF shielded chamber) and they installed an FM200 based fire suppression system in there. Supposedly, it is safe to use in populated areas, unlike Halon. My question there is how does it work? If it doesn't freeze the area or displace the o2 content, how does it put out a fire? I looked it up - I don't have it ALL in my head. in my summary: it is a liquefied gas, which works primarily by sucking the heat out of the room - it does have a frostbite hazard if you come in direct contact with the liquid agent, or a direct blast of the gas. it also, according to the data, is not safe for prolonged exposure, which ranges from a half minute at maximum planned concentration to 5 minutes at minimum planned concentration. I believe the agent then ventilates as an inert gas, or at least not toxic to people. www.janusfiresystems.com/products/fm-200my impression is it is essentially the same as Halon, except it doesn't deplete the ozone layer. - which is to say it is not directly toxic to humans, but it can still cause harm with massive exposure. - so "safe to use" means safe to have installed, but you still want to evacuate the area if it discharges. |
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Post by silverdragon on Oct 23, 2015 6:40:49 GMT
That is the question, if you "Hear" a Fire extinguisher discharging, or even see it happening through an air vent, how likely are you to "Abandon room" in quick time?...
Two CO2 extinguishers worth?...
When I did my ADR fire training, we let off a bit more than 2 cylinders worth, we HAD to go outside for elf-and-safe-tea reasons, but apart from "Dont breath it in" advice, even in an enclosed car park, we didnt worry overly much about the result?...
As for in a home, you would open a window?... vent the gas?...
Yeah right, you wouldnt want to be in a sealed room, but, I dont thing two cylinders worth are THAT dangerous in a well vented house?...
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Post by oscardeuce on Oct 23, 2015 23:32:15 GMT
You do not have to even displace the O2, just get the CO2 level to about 5%.
21% O2
5% Co2
74% N2 would be lethal if you were exposed long enough.
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Post by OziRiS on Oct 25, 2015 0:56:47 GMT
You do not have to even displace the O2, just get the CO2 level to about 5%. 21% O2 5% Co2 74% N2 would be lethal if you were exposed long enough. So, let's assume a small room (no furniture). 12x16x7 feet. That's 1344 cubic feet. How much co 2 would be needed to get a concentration of 5% in a room like that? My math is probably off, since I'm by no means a math geek, but a quick and dirty calculation gives me 67,2 cubic feet of co 2 in a gaseous state. What that translates to in canisters of compressed gas (extinguishers), I don't know. |
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Post by GTCGreg on Oct 25, 2015 1:37:53 GMT
You do not have to even displace the O2, just get the CO2 level to about 5%. 21% O2 5% Co2 74% N2 would be lethal if you were exposed long enough. So, let's assume a small room (no furniture). 12x16x7 feet. That's 1344 cubic feet. How much co 2 would be needed to get a concentration of 5% in a room like that? My math is probably off, since I'm by no means a math geek, but a quick and dirty calculation gives me 67,2 cubic feet of co 2 in a gaseous state. What that translates to in canisters of compressed gas (extinguishers), I don't know. You would need about 8 lbs of liquid CO 2. That would be a relatively small CO 2 fire extinguisher. www.airproducts.com/products/Gases/gas-facts/conversion-formulas/weight-and-volume-equivalents/carbon-dioxide.aspx |
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Post by silverdragon on Oct 25, 2015 2:07:54 GMT
Open that out to a three bed two bath sizeable living, with kitchen and hallway in "Suburbia" with possible good ventilation....
Also add on a "Paranoid" set of occupants....
Chances of no one noticing a "Hissing" noise out of an air-vent?... small to negligible.?..
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Post by OziRiS on Oct 25, 2015 12:02:02 GMT
So, let's assume a small room (no furniture). 12x16x7 feet. That's 1344 cubic feet. How much co 2 would be needed to get a concentration of 5% in a room like that? My math is probably off, since I'm by no means a math geek, but a quick and dirty calculation gives me 67,2 cubic feet of co 2 in a gaseous state. What that translates to in canisters of compressed gas (extinguishers), I don't know. You would need about 8 lbs of liquid CO 2. That would be a relatively small CO 2 fire extinguisher. www.airproducts.com/products/Gases/gas-facts/conversion-formulas/weight-and-volume-equivalents/carbon-dioxide.aspxOkay, so extrapolating further from that, a quick Google search told me that the average American house as of 2013 was around 2,600 ft 2 (source: money.cnn.com/2014/06/04/real_estate/american-home-size/) Our small room from the example was 192 ft 2, so, assuming a height of 7 ft in all rooms, we take the 2,600 ft 2 of the entire house, divide that by 192 and that comes to just under 13,5. Multiply that by the 8 lbs of liquid CO 2 from before and we get 108 lbs total. CO 2 fire extinguishers in the US seem to come in 2,5 lb, 5 lb, 10 lb, 15 lb and 20 lb canisters, so all that would take is five 20 lb extinguishers and a single 10 lb one. Again, the math on this was quick and dirty, so there are probably a ton of variables that could play a part in this. As SD points out, a lot would probably be lost to regular ventilation for one thing, so you might need to double the amount of extinguishers just to account for that, not to mention there might be rather complex stoichiometric equations (how the CO 2 mixes with the atmospheric air) to take into consideration. And I'd just like to point out that if it hadn't been for our good friends the MythBusters, I wouldn't even have known the word "stoichiometry" and that it's something worth considering in a situation like this  |
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Post by the light works on Oct 25, 2015 14:17:25 GMT
Okay, so extrapolating further from that, a quick Google search told me that the average American house as of 2013 was around 2,600 ft 2 (source: money.cnn.com/2014/06/04/real_estate/american-home-size/) Our small room from the example was 192 ft 2, so, assuming a height of 7 ft in all rooms, we take the 2,600 ft 2 of the entire house, divide that by 192 and that comes to just under 13,5. Multiply that by the 8 lbs of liquid CO 2 from before and we get 108 lbs total. CO 2 fire extinguishers in the US seem to come in 2,5 lb, 5 lb, 10 lb, 15 lb and 20 lb canisters, so all that would take is five 20 lb extinguishers and a single 10 lb one. Again, the math on this was quick and dirty, so there are probably a ton of variables that could play a part in this. As SD points out, a lot would probably be lost to regular ventilation for one thing, so you might need to double the amount of extinguishers just to account for that, not to mention there might be rather complex stoichiometric equations (how the CO 2 mixes with the atmospheric air) to take into consideration. And I'd just like to point out that if it hadn't been for our good friends the MythBusters, I wouldn't even have known the word "stoichiometry" and that it's something worth considering in a situation like this the average is skewed by the McMansion trend. 1300 square feet would be closer to the median home size. |
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Post by GTCGreg on Oct 25, 2015 20:58:37 GMT
Okay, so extrapolating further from that, a quick Google search told me that the average American house as of 2013 was around 2,600 ft 2 (source: money.cnn.com/2014/06/04/real_estate/american-home-size/) Our small room from the example was 192 ft 2, so, assuming a height of 7 ft in all rooms, we take the 2,600 ft 2 of the entire house, divide that by 192 and that comes to just under 13,5. Multiply that by the 8 lbs of liquid CO 2 from before and we get 108 lbs total. CO 2 fire extinguishers in the US seem to come in 2,5 lb, 5 lb, 10 lb, 15 lb and 20 lb canisters, so all that would take is five 20 lb extinguishers and a single 10 lb one. Again, the math on this was quick and dirty, so there are probably a ton of variables that could play a part in this. As SD points out, a lot would probably be lost to regular ventilation for one thing, so you might need to double the amount of extinguishers just to account for that, not to mention there might be rather complex stoichiometric equations (how the CO 2 mixes with the atmospheric air) to take into consideration. And I'd just like to point out that if it hadn't been for our good friends the MythBusters, I wouldn't even have known the word "stoichiometry" and that it's something worth considering in a situation like this the average is skewed by the McMansion trend. 1300 square feet would be closer to the median home size. Maybe 2600 sq ft is the average size of NEW homes being built, but I agree, if you consider EVERYTHING out there, 1300 would be a more reasonable number. As to the amount of CO 2 required to be dangerous, I don't thing we are talking that much. Any dry ice used for food packaging that is shipped on commercial airlines must be listed as to how much on a hazardous material manifest. The reason is that sometimes live animals are transported in the cargo holds. If there is too much dry ice, the CO 2 gas that is given off as it evaporates can kill the animals. It's happened. |
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Post by OziRiS on Oct 25, 2015 22:19:25 GMT
Okay, so we end up with half the calculated amount and end up with roughly three 20 lb extinguishers.
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Post by silverdragon on Oct 26, 2015 8:23:19 GMT
Glad to see we dont just waste time slacking jaws here?... No seriously.... I could have asked this question on many boards and I would have got "My mate who knows someone who knows someone says it will deffo kill ya!", and then a handbag war on semantics. Here, someone does the maths. Its not wasted. We all noticed. And if that is just my way of saying "Good job", then perhaps I should waste less words?.... Well done.  |
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Post by OziRiS on Oct 26, 2015 10:42:17 GMT
Glad to see we dont just waste time slacking jaws here?... No seriously.... I could have asked this question on many boards and I would have got "My mate who knows someone who knows someone says it will deffo kill ya!", and then a handbag war on semantics. Here, someone does the maths. Its not wasted. We all noticed. And if that is just my way of saying "Good job", then perhaps I should waste less words?.... Well done. Thanks, but there are still variables we haven't accounted for. As you said earlier, ventilation comes into play. A regular house isn't hermetically sealed. If it was, we'd constantly have to have a window open to allow new air to flow in, so we don't suffocate in our bedrooms while sleeping. I think the only way to tell for sure how much CO 2 would be needed is to test it, but seeing as the show is dying, Adam and Jamie certainly won't be doing it and I don't see any of us having the time and money to buy 6-10 20 lb extinguishers and the equipment needed to measure its concentration in the air and clearing out our homes for a day to do this safely... All we have is a theoretical estimate. Without practical testing, that's about as good as "my mate knows someone who knows someone who says...". |
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Post by the light works on Oct 26, 2015 14:28:39 GMT
Glad to see we dont just waste time slacking jaws here?... No seriously.... I could have asked this question on many boards and I would have got "My mate who knows someone who knows someone says it will deffo kill ya!", and then a handbag war on semantics. Here, someone does the maths. Its not wasted. We all noticed. And if that is just my way of saying "Good job", then perhaps I should waste less words?.... Well done. Thanks, but there are still variables we haven't accounted for. As you said earlier, ventilation comes into play. A regular house isn't hermetically sealed. If it was, we'd constantly have to have a window open to allow new air to flow in, so we don't suffocate in our bedrooms while sleeping. I think the only way to tell for sure how much CO 2 would be needed is to test it, but seeing as the show is dying, Adam and Jamie certainly won't be doing it and I don't see any of us having the time and money to buy 6-10 20 lb extinguishers and the equipment needed to measure its concentration in the air and clearing out our homes for a day to do this safely... All we have is a theoretical estimate. Without practical testing, that's about as good as "my mate knows someone who knows someone who says...". In the US, to get the highest possible efficiency rating on a house, it is built so tightly that you then have to install a fan that runs 24 hours a day, forcing fresh air in and stale air out |
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Post by GTCGreg on Oct 26, 2015 16:01:43 GMT
In the US, to get the highest possible efficiency rating on a house, it is built so tightly that you then have to install a fan that runs 24 hours a day, forcing fresh air in and stale air out I've seen these systems. My question, is the efficiency rating before or after the fan is installed and operating? |
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Post by the light works on Oct 26, 2015 16:06:45 GMT
In the US, to get the highest possible efficiency rating on a house, it is built so tightly that you then have to install a fan that runs 24 hours a day, forcing fresh air in and stale air out I've seen these systems. My question, is the efficiency rating before or after the fan is installed and operating? I'm inclined to think it is all on paper, and doesn't include the cost of running the fan, or of rebuilding the house after the walls rot from the inside out. |
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