Are officials in the fire industry considering using liquid nitrogen to put out fires? What would be some of the complications to the storage, distribution and application of this substance? Even if this was a valid resource, I understand it would not be used on every house fire or every car fire, for obvious reasons. But some burning buildings, being unsalvageable and also that pose a threat to exposures, would be a candidate for this type of radical approach, no?
I do not know, and I presume some Smart Person will be along shortly who does know. But …
First off the average firefighter needs an average method of putting out fires. That is to say, he can find almost any sort of fire when he answers a call, and water while not perfect works pretty well and is cheap.
Next, I presume liquid N would turn to the gaseous form darn quickly. That is it would (I think) expand very fast. That is, it would explode on contact with something hot.
Failing that, I presume most hot things (hot steel for example) would contract darn fast when hit with liquid N. I presume many or most materials would behave poorly under that sort of abuse.
Humans also would not want to be hit with the stuff. Look how wet firefighters are at a firefield (like my new word? Thanks DanceswithCats!). If all that water was liquid N there would be some real problems.
Next it is not too cheap (about a dollar a gallon last time I looked).
Still it might have some sort of specialized application.
I think fireground is the usual term.
I’d think a better use for liquid N2 would be in building sprinkler systems for the reasons Paul detailed.
Density, Liquid @ BP, 1 atm: 50.45 lb/scf
Density, Gas @ 68°F (20°C), 1 atm: 0.0725 lb/scf
link
Nitrogen expands seven hundred fold when heated to normal atmospheric pressure. Also, nitrogen in gas form is an asphyxiant. A relatively small spill while fighting a fire could suffocate a lot of firefighters.
That said, liquid nitrogen is used for fighting oilwell blowouts (I think that Red Adair pioneered its use), but that’s a specialized form of firefighting where the emphasis is on being completely prepared for the job instead of quickly putting out the fire.
Which would also put out the fires . . . an ultra-cold substance that denies the fire oxygen would work quite well, aside from destroying whatever’s left of the property in the room and killing the firefighters.
I have worked with liquid nitrogen, and apart from some very niche applications, it would not be efficient at all to use in fighting fires. Transporting LN2 requires specialized vessels to control temp and pressure. The commonly used industry containers can hold about 180 liters for a couple of weeks before venting out more or less completely.
As for it’s application, as noted, it is an asphyxiant because it displaces the O2 in the air. So theoretically if you had a fire in a confined space, you could pump LN2 in there, it would vaporize and smother the fire. Just make sure noone is in said confined space. The fact that it’s very cold has nothing to do with it’s ability to put out a fire. However the fact that it is very cold will have an effect on whatever you spray it on; it’s entirely possible that pumping it over a hot object in a fire might cause said object to shatter. Even metal pipes could be vulnerable to this effect.
I get a little annoyed when I hear things like this. Obviously the fact that ANYTHING is very cold would have something to do with its ability to put out a fire. Things that have low temperatures would tend to reduce the temperature of anything they come into contact with, and any flammable material has a ‘kindling point’ or some such below which temperature it will not burn.
The cold effect may not be significant compared to the oxygen displacement effect (which is another good way to put out a fire,) but surely it has some effect.
You’ve been watching The Transformers:Generation One, haven’t you?
That scene with Ironhide?
What would really have an effect would be a gas that could displace oxygen and simultaneously interfere with the combustion reaction.
Halon fit this bill for years. It worked like a charm, and every ship I ever served on in the Navy had a system in place to flood the engine room with halon in case of a massive fuel oil fire.
Unfortunately, halon has been determined to be an environmental hazard, and they aren’t making it any more.
Water is free, easily available, and can be stored without an insulated/refrigerated container. Case closed.
Everyone’s overlooked gaseous nitrogen? Guess I’m the only one here that’s been in server rooms and seen hand-held compressed nitrogen extinguishers or the man-sized “deluge” tanks. In gas form, nitrogen works very nicely at putting out class B and C fires (liquids and live electric) but is only fair at class A. It can actually be dangerous when used on something like a trash can fire as the gas can simply blow burning stuff around and spread the fire.
So, it looks like the cons of nitrogen outweigh the pros for random fires. It’s expensive, human exposure can be fatal, it might shatter whatever’s on fire, and it can spread burning material.
In specialized uses, it is good stuff though - you don’t want to pour water into a server room or telecom facility - between AC line power and UPS backups, there’s electricity all over the place that generally has no easy centralized means of shutoff, and computers, amazingly enough, are not waterproof.
I am curious about the oil well fires - I’ve seen how they use dynamite - the explosion consumes all the oxygen in the area and snuffs the fire, leaving a non-burning spray of oil. I’ve not seen any mention of nitrogen, though.
Halon didn’t just displace oxygen. The heat of the fire caused the Halon to break down into constiuents that gobbled oxygen where the heat was. The advantage was that it put out the fire while still allowing oxygen levels that would support life.
Liquid CO2 IS used extensivly for fire fighting. It can be stored at room temperature at 200 psi or so. LN2 requires crogenic storage.
Far from damaging a building, CO2 is used to AVOID damage that would result if a fire were extinguished with water, or even dry chemicals (which make a huge mess).
cite please?
Pumped in, it probably wouldn’t do that much damage to a structure or what’s inside. I could see a big problem with controlling the gas, especially in an urban setting where the gas could spill out of the building and suffocate people who thought that they were a safe distance away.
gotpasswords, Wow. Until I searched, I thought that dynamite had been replaced by water and N2 for extinguishing blowouts. I think that these were used overwhelmingly in Kuwiat, mainly because of the large number of wells that needed to be capped. I guess that there isn’t that much water around the typical blowout.
Really? Then you pay my water bill.
Hopefully, one of the resident firefighters will stop by and put us all straight, but it’s worth noting that to put out a fire you have to do more than simply remove the oxygen; you have to cool the area so that once you reintroduce oxygen it doesn’t reignite.
BTW the server room at work has water sprinklers. They’ve taken the view that if there’s a fire then the equipment’s going to be damaged anyway so added water isn’t a problem as they’ll be replacing the kit. It’s the data that’s important, and that’s backed up regularly.
I’m not exactly sure what part of my post required a cite… (it kinda seems self-evident, but I know that doesn’t necessarily mean it’s all true.) I’ll start with a cite from the master, though:
http://www.straightdope.com/columns/021122.html
It would seem to me that fighting a fire by trying to deprive it of two essential ingredients is better than just blocking out one. (In most cases, trying to remove the fuel without the fire just following it would prove to be remarkably tricky.)
well, not heat, but a spark is neccessary to start a fire. I will admit that if you cool certain things like volatile liquids you will reduce the amout that is vaporized and perhaps limit the fuel source.
But this is really beside the point. If you are pumping LN2 into a fire, the LN2 is going to vaporize pretty much immediately in the presence of heat. When we used to fill LN2 vessels, when they got too full they would spit LN2. These droplets never made it to the ground before they were vaporized by atmospheric heat. If you stood next to the container you might get some small droplets of LN2 on you, but you had to be pretty close.
I do not think it’s self evident that cooling things will put out a fire. It may mitigate various fuels from vaporizing and combusting, but that’s it unless you have evidence to prove me wrong.
Resident firefighter here. The classic ‘fire triangle’ composed of fuel, heat, and oxygen has been replaced by the ‘fire tetrahedron’ and includes the three mentioned as well as chemical reaction.
The application of dihydrogen monoxide typically accomplishes the exclusion of oxygen together with the removal of heat by using that heat to effect conversion from a liquid to a gaseous state, which also causes a volumetric expansion of approximately 1700x, which does some oxygen excluding.
Use of a CO[sub]2[/sub] extinguisher does the job in similar fashion, sans expansion owing to physical state conversion.
Halon® was the product which upset the traditional triangle theory, as it interrupts the combustion process, without all of the nasty drawbacks associated with other extinguishing agents.
The Class D or flammable metal fire is extinguished by application of an agent which encapsulates the burning material, denying oxygen and offering a slight cooling value.
BTW Quartz, those heads may look like ordinary wet pipe sprinkler devices, but the agent behind them isn’t necessarily water. Halon® has been replaced with more environmentally friendly agents.
[Minor Nitpick for krisolov] While true that a spark can ignite many different materials, I submit that they may also be raised to their autoignition temperature in the absence of a spark, and will burn very nicely. [/MNP]
Quite, however, in our case it’s definitely water. Equipment is expendable; people aren’t.