Liquid Nitrogen used to fight fires?

[hauss]

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?

[Paul in Qatar]

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.

[jnglmassiv]

Originally Posted by Paul in Saudi

Look how wet firefighters are at a firefield (like my new word? Thanks DanceswithCats!)

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.

[cornflakes]

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.

[Excalibre]

Originally Posted by cornflakes

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.

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.

[krisolov]

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.

[chrisk]

Originally Posted by krisolov

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.

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.

[Bosda Di'Chi of Tricor]

Originally Posted by hauss

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?

You've been watching The Transformers:Generation One, haven't you?

That scene with Ironhide?

[Mr. Moto]

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.

[RealityChuck]

Water is free, easily available, and can be stored without an insulated/refrigerated container. Case closed.

[gotpasswords]

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.

[Kevbo]

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.

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).

[krisolov]

Originally Posted by chrisk

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.

cite please?

[cornflakes]

Originally Posted by cornflakes

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.

Originally Posted by Excalibre

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.

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.

[Odinoneeye]

Originally Posted by RealityChuck

Water is free, easily available, and can be stored without an insulated/refrigerated container. Case closed.

Really? Then you pay my water bill.

[Quartz]

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.

[chrisk]

Originally Posted by krisolov

cite please?

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:

Originally Posted by Cecil Adams

Rapid combination of oxygen with fuel in the presence of heat. Oxygen, fuel, and heat are the essential ingredients of fire.

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.)

[krisolov]

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.

[danceswithcats]

Originally Posted by Quartz

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.

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 CO₂ 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]

[Quartz]

Originally Posted by danceswithcats

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.

Quite, however, in our case it's definitely water. Equipment is expendable; people aren't.

[krisolov]

[QUOTE/]
[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][/quote]

I agree completely and stand corrected.

What do you think about the cooling effect LN2 would have on a fire? Significant or not so?

[KCB615]

One of the other resident firefighters checking in-


RealityChuck put it best - water is cheap, easy to move, and plentiful. How much does 1000 gallons of liquified nitrogen cost? I know that much water (if we had to pay for it to put a fire out) costs about $1.60 in my community. Nitrogen may be plentiful, but not that cheap.

I also have a difficult time figuring out how I would go about deploying a hoseline filled with liquified nitrogen, and fear even more how my firefighters are going to not get the stuff on them. Every agent I have used; water, foam, dry chemical, halon, halotron, dry powder, and CO2 has gotten on either me or a member of my crew. None of the agents listed will cause harm to a firefighter in his/her normal protective clothing (as long as they're on-air), and we can just wash it off when we get outside. Liquified nitrogen, on the other hand, will cause some significant damage to both my gear and myself.

As for the sprinkler system in the computer server room - it is very possible that the system is a preaction system, not a normal wet system. In a preaction system, the piping is full of air at atmospheric pressure, and the sprinkler heads are closed. If two or more detectors (smoke, heat, or flame) activate, or a single pull station, the preaction valve will open, allowing water into the piping, but not flowing from the heads - essentially turning the preaction system into a wet system. The heads nearest the fire will fuse (like on a normal wet system) from the heat of the fire, and thus dumping the water on the fire.

Preaction systems are becoming quite common in rooms where you don't want the expense of a clean agent system (halotron, FM200, Inergen, etc), but also don't want the water damage from a leaking or accidentally opened wet system.

[danceswithcats]

Originally Posted by krisolov

What do you think about the cooling effect LN2 would have on a fire? Significant or not so?

I'm not aware of any studies or other modeling that has been performed on fire behavior and the effecacy of LN2, so while I'd presume it to be an effective coolant, other agents outweigh it when a cost/benefit analysis is done. The inherent hazards also discourage it's use-we've got enough going on that's ugly with a simple room and contents burn.

[buttonjockey308]

Another Firefighter checking in. LN2 is, as many have pointed out, a cryogenic liquid. The use of it (we'll just assume there are pumps with the ability to deliver all you'd need to actually fight a typical room-and-contents type of fire) would create a whole new set of hazards both in supression systems and in delivered applications. Imagine fighting a hot room fire, only to burn youself AFTER the fire was put out. It seems that the term "NFPA" is applicable because there is No Fecking Practical Application to LN2 as a common firefighting agent.

Water will continue to be the method of choice for extinguinshing common, AB and C class fires.

[Squink]

Liquid nitrogen has a low heat capacity (~0.00025 kcal/g°K) and low heat of vaporization(0.05 kcal/g). That makes it a poor cooling agent. You can put your hand in a vat of LN₂, and pull it out without damage.

[chrisk]

Originally Posted by krisolov

I do not think it's self evident that cooling things will put out a fire.

For the record, I'm not saying that cooling the fuel will always put out the fire, just that it is an effect that will push the fire towards its death. If you have a big enough fire, it is generating a lot of heat, and that can obviously 'push back' and cancel out the cooling effect.

The point was simply that low temperatures are a factor, not that they're a winning trump every time.

[Mycroft H.]

Originally Posted by danceswithcats

The application of dihydrogen monoxide typically accomplishes the exclusion of oxygen together with the removal of heat…

Oh no, the dangerous dihydrogen monoxide raises its ugly head again.

[fortytwo]

Some military aircraft have used Nitrogen (gas) as a fire suppressant in fuel tanks for many years. Perhaps because of a possible vulnerability when under hostile fire.
Also aircraft tyres are commonly inflated with it.

[Mr. Moto]

Car tires are routinely inflated with a gaseous mixture composed of 78% gaseous nitrogen.