# liquid nitrogen fire **URL:** \ **Category:** Factual Questions\ **Created:** [January 21, 2009, 9:31pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360 "2009-01-21T21:31:56Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![john\_alford](https://avatars.discourse-cdn.com/v4/letter/j/bcef8e/32.png) [@john\_alford](https://boards.straightdope.com/u/john_alford)\ **Post date:** [January 21, 2009, 9:31pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/1 "2009-01-21T21:31:56Z")
hi i’m trying to figure out without actually testing it myself could liquid nitrogen put out a fire. ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [January 21, 2009, 10:20pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/2 "2009-01-21T22:20:39Z")
Welcome to the SDMB, John. Since this doesn’t seem to be a comment on one of Cecil’s columns, I’ll move this thread to General Questions, our forum for factual queries. bibliophage moderator CCC ---
**Author:** ![garygnu](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garygnu/32/2924_2.png) [@garygnu](https://boards.straightdope.com/u/garygnu)\ **Post date:** [January 21, 2009, 10:24pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/3 "2009-01-21T22:24:48Z")
Probably, depending on the size of the fire. Fire needs fuel, oxygen, and heat. Liquid Nitrogen would do a pretty good job of removing heat. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 21, 2009, 10:30pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/4 "2009-01-21T22:30:12Z")
And also a pretty good job of removing oxygen. ---
**Author:** ![Will\_Repair](https://avatars.discourse-cdn.com/v4/letter/w/a698b9/32.png) [@Will\_Repair](https://boards.straightdope.com/u/Will_Repair)\ **Post date:** [January 21, 2009, 10:30pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/5 "2009-01-21T22:30:49Z")
Can’t think of a reason it wouldn’t. If it stayed a liquid then it would act like water. If it converted to gas it would still smother the fire. Both states would deprive the fuel of oxygen, and possibly heat. All this assumes enough liquid nitrogen since you can put out a house fire with a blanket (a really big blanket.) ---
**Author:** ![Gbro](https://avatars.discourse-cdn.com/v4/letter/g/c6cbf5/32.png) [@Gbro](https://boards.straightdope.com/u/Gbro)\ **Post date:** [January 21, 2009, 10:37pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/6 "2009-01-21T22:37:03Z")
You would have a hard time keeping the nitrogen in a liquid state. May times while waiting for a part to cool in liquid nitrogen we would have time to play:D. Just to see how far into the container we could lower a burning match, burning cigarette, before the nitrogen would displace the O2, and on the ground around the container while the gas spills out. I have thought introducing liquid nitrogen into a garbage dump (years back) would be effective in controlling the vermin. ---
**Author:** ![cornflakes](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@cornflakes](https://boards.straightdope.com/u/cornflakes)\ **Post date:** [January 21, 2009, 10:37pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/7 "2009-01-21T22:37:15Z")
It’s used to put out oilwell blowouts. It works well on the smaller ones as well. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [January 21, 2009, 10:37pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/8 "2009-01-21T22:37:50Z")
> [@Will\_Repair](#): > > If it converted to gas it would still smother the fire. That depends on what is burning. Magnesium metal will burn in pure nitrogen to produce magnesium nitride. Aluminum will also burn in N[sub]2[/sub], but iron will not. ---
**Author:** ![WF\_Tomba](https://avatars.discourse-cdn.com/v4/letter/w/d9b06d/32.png) [@WF\_Tomba](https://boards.straightdope.com/u/WF_Tomba)\ **Post date:** [January 21, 2009, 10:37pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/9 "2009-01-21T22:37:55Z")
Depending on the conditions of the fire, some of the nitrogen might itself react with the oxygen and produce nitrogen oxides, which you wouldn’t want to breathe. ---
**Author:** ![scm1001](https://avatars.discourse-cdn.com/v4/letter/s/c4cdca/32.png) [@scm1001](https://boards.straightdope.com/u/scm1001)\ **Post date:** [January 21, 2009, 10:59pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/10 "2009-01-21T22:59:47Z")
there is some interest in using liquid nitrogen in putting out real fires and has been tested with a full scale fire engine [http://www.innovations-report.de/html/berichte/biowissenschaften\_chemie/bericht-34911.html](http://www.innovations-report.de/html/berichte/biowissenschaften_chemie/bericht-34911.html). There are some sort of fun videos exploring the idea [Frostbite Theater - Liquid Oxygen and Fire!](http://education.jlab.org/frost/combustion.html)[http://www.youtube.com/watch?v=Yex063\_Fblk](http://www.youtube.com/watch?v=Yex063_Fblk) ---
**Author:** ![scm1001](https://avatars.discourse-cdn.com/v4/letter/s/c4cdca/32.png) [@scm1001](https://boards.straightdope.com/u/scm1001)\ **Post date:** [January 21, 2009, 11:01pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/11 "2009-01-21T23:01:03Z")
> [@WF\_Tomba](#): > > Depending on the conditions of the fire, some of the nitrogen might itself react with the oxygen and produce nitrogen oxides, which you wouldn’t want to breathe. hmm there is always lots of nitrogen in the air so I doubt whether this is really a problem ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 21, 2009, 11:05pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/12 "2009-01-21T23:05:40Z")
Also, even if some things can react with nitrogen, they’ll probably do so a lot less energetically than with oxygen. ---
**Author:** ![WF\_Tomba](https://avatars.discourse-cdn.com/v4/letter/w/d9b06d/32.png) [@WF\_Tomba](https://boards.straightdope.com/u/WF_Tomba)\ **Post date:** [January 21, 2009, 11:08pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/13 "2009-01-21T23:08:59Z")
> [@scm1001](#): > > hmm there is always lots of nitrogen in the air so I doubt whether this is really a problem Well, I know car engines can produce a certain amount of nitrogen oxides. Maybe that’s because the reaction is occurring under pressure? I don’t really know what conditions cause it to happen. ---
**Author:** ![Will\_Repair](https://avatars.discourse-cdn.com/v4/letter/w/a698b9/32.png) [@Will\_Repair](https://boards.straightdope.com/u/Will_Repair)\ **Post date:** [January 22, 2009, 12:04am UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/14 "2009-01-22T00:04:01Z")
> [@Squink](#): > > Magnesium metal … … or carbon dioxide. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [January 22, 2009, 1:31am UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/15 "2009-01-22T01:31:23Z")
Nitrogen gas is one of the most stable molecules around. It’s notoriously difficult to split apart thanks to its triple bond. That’s why fertilizers are used to get nitrogen into plants in a usable form. That’s also why so many explosives are nitrogen based. They release nitrogen gas, and in dropping down to that low energy level, they release lots of heat. Anyway, I don’t think you’re going to get a lot of dangerous nitrogen species under most conditions. ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [January 22, 2009, 2:03am UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/16 "2009-01-22T02:03:40Z")
The magnesium nitrogen reaction is weak enough that I suspect enough liquid nitrogem will cool it down to not reacting. I don’t even know that magnesium can react with nitrogen in it’s liquid state. Nitrogen oxides require oxygen which will be quickly dispersed by the expanding nitrogen. You may initially get some nitrogen oxides, but not a lot. Generally, I think liquid nitrogen would be very good at putting out most fires if you had enough of it. Depending on the size of the room and fire, I wonder if suffocation might be a hazard. ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [January 22, 2009, 3:34am UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/17 "2009-01-22T03:34:08Z")
> [@WF\_Tomba](#): > > Well, I know car engines can produce a certain amount of nitrogen oxides. Maybe that’s because the reaction is occurring under pressure? I don’t really know what conditions cause it to happen. Sort of. The main determinants of how NOx forms in combustion are a combination of factors, involving such things as stoichiometry, turbulence, temperature and time. Temperature is probably by far the greatest of these factors for NOx production, with a spike at atmospheric pressures starting near the 2300F mark (note this varies due to many factors). Liquid nitrogen dumped on a fire is unlikely IMO to produce a substantial amount of NOx due to the relatively low resulting temperature of the nitrogen. ---
**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\ **Post date:** [January 22, 2009, 2:59pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/18 "2009-01-22T14:59:49Z")
Should work, both for cooling and as a barrier to oxygen, though nitrogen won’t work quite as well as carbon dioxide or other fire suppressant gases that work by displacing oxygen near the fire. Dedicated fire suppressants are going to be heavier than air so that they settle down on top of the fire rather than drifting away. Nitrogen is pretty much exactly the same weight as air, so it will disperse a little more quickly than Halon or equivalents. ---
**Author:** ![Dag\_Otto](https://avatars.discourse-cdn.com/v4/letter/d/439d5e/32.png) [@Dag\_Otto](https://boards.straightdope.com/u/Dag_Otto)\ **Post date:** [January 22, 2009, 3:34pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/19 "2009-01-22T15:34:36Z")
> [@Quercus](#): > > Should work, both for cooling and as a barrier to oxygen, though nitrogen won’t work quite as well as carbon dioxide or other fire suppressant gases that work by displacing oxygen near the fire. Dedicated fire suppressants are going to be heavier than air so that they settle down on top of the fire rather than drifting away. Nitrogen is pretty much exactly the same weight as air, so it will disperse a little more quickly than Halon or equivalents. Using liquid nitrogen, as stated in the OP, is also going to scatter whatever is burning as it flashes to a gas. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [January 22, 2009, 3:45pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360/20 "2009-01-22T15:45:18Z")
> [@Dag\_Otto](#): > > Using liquid nitrogen, as stated in the OP, is also going to scatter whatever is burning as it flashes to a gas. Plus, if the fire is big enough, you might get some hellacious overpressures. [Next page](https://boards.straightdope.com/t/liquid-nitrogen-fire/482360.md?page=2)