# Liquid nitrogen canisters on sidewalk **URL:** \ **Category:** Factual Questions\ **Created:** [August 9, 2001, 6:07pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634 "2001-08-09T18:07:19Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![John\_Kentzel-Griffin](https://avatars.discourse-cdn.com/v4/letter/j/ccd318/32.png) [@John\_Kentzel-Griffin](https://boards.straightdope.com/u/John_Kentzel-Griffin)\ **Post date:** [August 9, 2001, 6:07pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/1 "2001-08-09T18:07:19Z")
I’ve noticed big metal canisters (4797 cubic feet) of liquid nitrogen gas on the sidewalk at several corners in Manhattan. On the corner where I work, there are always two or three of them. One has a rubber tube leading into a manhole cover that says E C S Co Ltd. I think some of them have leaks; there is ice and frost on the side. One of them had a label that said “Warning: contains human souls” :eek: What are they for? Isn’t a leaking gas canister dangerous, especially sitting out in the hot sun? ---
**Author:** ![Jukeball](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@Jukeball](https://boards.straightdope.com/u/Jukeball)\ **Post date:** [August 9, 2001, 6:17pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/2 "2001-08-09T18:17:59Z")
Here is another one like you. Guess what they are probably used for registering traffic. Check this link out. [http://www.wickedfresh.com/archive/may01/](http://www.wickedfresh.com/archive/may01/) ---
**Author:** ![Jargent](https://avatars.discourse-cdn.com/v4/letter/j/48db29/32.png) [@Jargent](https://boards.straightdope.com/u/Jargent)\ **Post date:** [August 9, 2001, 6:22pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/3 "2001-08-09T18:22:59Z")
In Time Out New York a few weeks ago they addressed this. > [@](#): > > What are those nitrogen tanks you see on street corners? > > Because moisture from steam and heating systems can damage underground phone lines, Verizon uses nitrogen to help keep its cables dry. Stored in liquid form at -300ºF in pressurized 40-gallon tanks dotting city streets, the nitrogen is slowly delivered belowground by a small rubber tube threaded through a manhole cover. Once released, the nitrogen “heats up”; at -280ºF, it becomes gas. The pressure pushes it into Verizon’s three-inch voice and data cables—some of which house more than 7,000 copper wires—where it travels along the lines, keeping them dry before dissipating. > > The difference in pressure between the interior of a tank and the atmosphere causes the canister’s metal exterior to become cold, often frosting over. (Each tank lasts just one to three days before it must be replaced; large flatbed trucks tote the empties to a refill plant.) And just in case you are compelled to cool off by touching one on a scorching summer day, you’ll be happy to know that the canisters won’t harm you. In fact, they present little possibility for pedestrian danger: Nitrogen is nonexplosive, and the tanks, although under pressure, can take quite a beating. One Verizon maintenance worker admits, “We’ve even had them hit by cars.”—Justin Bishop Cite: > **[Time Out New York | New York Events and Things To Do All Year](https://www.timeout.com/newyork)** > > Your ultimate guide to New York for tourists and locals alike. Discover superb restaurants, amazing bars, great things to do and cool events in NYC. The rest of the article is worth reading too, really interesting stuff on how the city runs. ---
**Author:** ![Balance](https://avatars.discourse-cdn.com/v4/letter/b/ccd318/32.png) [@Balance](https://boards.straightdope.com/u/Balance)\ **Post date:** [August 9, 2001, 6:30pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/4 "2001-08-09T18:30:53Z")
I’m not sure what they would be for specifically, but cooling something or pressurizing cables–I know it’s sometimes used with heliax, although dehumidified air is more common. Fortunately, leaky nitrogen containers aren’t particularly dangerous, since the stuff is about as explosive as a stack of snails. The only problem is if the gas pools in a low place–it could asphyxiate someone who lacked an air source. (I see in preview that the function’s been covered–at least I can offer something on the safety issue.) ---
**Author:** ![MinkMan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/minkman/32/19170_2.png) [@MinkMan](https://boards.straightdope.com/u/MinkMan)\ **Post date:** [August 9, 2001, 7:04pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/5 "2001-08-09T19:04:50Z")
I can think of two possible uses for a large container of liquid nitrogen on a sidewalk with hoses leading to a manhole. First, they could be using it to create a freeze seal (for example see [http://www.freezesealinc.com](http://www.freezesealinc.com)) on a pipe in the manhole. The liquid N[sub]2[/sub] is used to freeze an ice plug in the pipe to allow it to be cut an welded on downstream of the freeze. This is done if the placement of isolation valve in the pipe does not allow the area to be worked on to be easily isolated and drained. A second reason I can think of would be to use an inert gas like nitrogen to flush and fill a pipe prior to working on it. Perhaps it’s being used on a pipe that carries natural gas of some other flamable substance and they want to weld on it with blowing themselves to bits. (On preview, it looks like Jargent has the best answer) ---
**Author:** ![Myrr21](https://avatars.discourse-cdn.com/v4/letter/m/e495f1/32.png) [@Myrr21](https://boards.straightdope.com/u/Myrr21)\ **Post date:** [August 9, 2001, 7:19pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/6 "2001-08-09T19:19:13Z")
> [@](#): > > The only problem is if the gas pools in a low place–it could asphyxiate someone who lacked an air source. Fortunately, nitrogen doesn’t so much “pool” the way heavier gasses do. Given that air is mostly nitrogen, and that most of what’s left is heavier than nitrogen, nitrogen gas itself certainly isn’t going to be heavier than air. Now, that’s not to say that you couldn’t flush too much air out of an enclosed space and suffocate, but it would take some doing. ---
**Author:** ![bughunter](https://avatars.discourse-cdn.com/v4/letter/b/aeb1de/32.png) [@bughunter](https://boards.straightdope.com/u/bughunter)\ **Post date:** [August 9, 2001, 7:27pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/7 "2001-08-09T19:27:50Z")
The real problem with exposed LN is that it will condense liquid Oxygen (LOX) out of the atmosphere, and LOX is [very reactive](http://ghg.ecn.purdue.edu/~ghg/). But this setup doesn’t sound like it carries much of a risk of this. Also, I’m surprised they’re leaving these dewars out in the open, so conspicuously. I wonder how long until teenagers find out how much fun the stuff is and start making off with the tanks? ---
**Author:** ![Jargent](https://avatars.discourse-cdn.com/v4/letter/j/48db29/32.png) [@Jargent](https://boards.straightdope.com/u/Jargent)\ **Post date:** [August 9, 2001, 7:34pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/8 "2001-08-09T19:34:37Z")
> [@](#): > > \*Originally posted by bughunter \* > \*\*Also, I’m surprised they’re leaving these dewars out in the open, so conspicuously. I wonder how long until teenagers find out how much fun the stuff is and start making off with the tanks? \*\* There’s an interesting side discussion: What happens when teens try to get high off nitrogen at -300 degrees? Reminds me of an old News of the Weird or Darwin Awards column I can’t find about teens inflating their colons with bicycle pumps. ---
**Author:** ![Jargent](https://avatars.discourse-cdn.com/v4/letter/j/48db29/32.png) [@Jargent](https://boards.straightdope.com/u/Jargent)\ **Post date:** [August 9, 2001, 7:39pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/9 "2001-08-09T19:39:23Z")
> [@](#): > > \*Originally posted by Jargent \* > \*\*Reminds me of an old News of the Weird or Darwin Awards column I can’t find about teens inflating their colons with bicycle pumps. \*\* Got bored. Found it. Enjoy. [http://www.darwinawards.com/legends/legends1998-06.html](http://www.darwinawards.com/legends/legends1998-06.html) ---
**Author:** ![Balance](https://avatars.discourse-cdn.com/v4/letter/b/ccd318/32.png) [@Balance](https://boards.straightdope.com/u/Balance)\ **Post date:** [August 9, 2001, 7:50pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/10 "2001-08-09T19:50:24Z")
> [@](#): > > \*Originally posted by Myrr21 \* > Fortunately, nitrogen doesn’t so much “pool” the way heavier gasses do. At STP, nitrogen won’t pool–but extremely cold gaseous nitrogen (say, just-evaporated from N[sub]L[/sub]) may under some circumstances, because it’s denser than the air around it. This may be something of a concern if it’s being piped down into a hole in the ground. ---
**Author:** ![manhattan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/manhattan/32/7_2.png) [@manhattan](https://boards.straightdope.com/u/manhattan)\ **Post date:** [August 9, 2001, 8:35pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/11 "2001-08-09T20:35:01Z")
> [@](#): > > \*Originally posted by bughunter \* > \*\* I wonder how long until teenagers find out how much fun the stuff is and start making off with the tanks? \*\* They’d have to _really_ want it. Most of these aren’t the skinny 5-foot tall ones with the nipple on top. They’re 6+ feet tall and four feet around and look like they weigh a billion pounds. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [August 9, 2001, 9:46pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/12 "2001-08-09T21:46:27Z")
Also those tanks are used to freeze oil in pipes that have cable (either telephone or electric). The oil prevents the cable from rusting and prevents the pipes from collection water. If repair to the cables are needed the oil must be frozen on both sides to prevent the oil from draining. ---
**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:** [August 9, 2001, 11:58pm UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/13 "2001-08-09T23:58:41Z")
> [@](#): > > \*Originally posted by Jargent \* > \*\* > > > [@](#): > > > > \*Originally posted by bughunter \* > > \*\*Also, I’m surprised they’re leaving these dewars out in the open, so conspicuously. I wonder how long until teenagers find out how much fun the stuff is and start making off with the tanks? \*\* > > There’s an interesting side discussion: What happens when teens try to get high off nitrogen at -300 degrees?\*\* Nothing. You maybe are confusing nitrogen (N[sub]2[/sub]) with nitrous oxide? ---
**Author:** ![bughunter](https://avatars.discourse-cdn.com/v4/letter/b/aeb1de/32.png) [@bughunter](https://boards.straightdope.com/u/bughunter)\ **Post date:** [August 10, 2001, 1:14am UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/14 "2001-08-10T01:14:03Z")
The stuff is fun not when you inhale it (though I don’t really know for sure, I never tried). It’s fun when you dunk things like bugs in it. Or inflated balloons. Or bananas. Or flowers. Try a superball sometime! Or, if you’re not as geeky as that… when you pour it on unsuspecting passersby from a third story window. Or when you dunk your neighbor’s yap dog in it. ---
**Author:** ![Chas.E](https://avatars.discourse-cdn.com/v4/letter/c/e99b99/32.png) [@Chas.E](https://boards.straightdope.com/u/Chas.E)\ **Post date:** [August 10, 2001, 2:33am UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/15 "2001-08-10T02:33:58Z")
> [@](#): > > \*Originally posted by bughunter \* > **The stuff is fun not when you inhale it (though I don’t really know for sure, I never tried).** You don’t have to try, you’re inhaling 78% nitrogen right now. Breathing 100% nitrogen for a while would give you a slight buzz from lack of oxygen, then you’d pass out and eventually die of asphyxiation if your normal air supply wasn’t restored. Ah, I see Anthracite is with us, welcome back… Do you happen to have a CRC Table book handy? Or perhaps you’d know this off the top of your head. Due to bughunter’s question, I’m curious about the liquification points of nitrogen and oxygen. ---
**Author:** ![Jargent](https://avatars.discourse-cdn.com/v4/letter/j/48db29/32.png) [@Jargent](https://boards.straightdope.com/u/Jargent)\ **Post date:** [August 10, 2001, 2:43am UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/16 "2001-08-10T02:43:05Z")
> [@](#): > > \*\* > > > [@](#): > > > > \*Originally posted by Jargent \* > > **There’s an interesting side discussion: What happens when teens try to get high off nitrogen at -300 degrees?** > > Nothing. You maybe are confusing nitrogen (N[sub]2[/sub]) with nitrous oxide? \*\* Not confusing the two, just making a different point. Sure nothing is going to happen when you inhale Nitrogen. As someone pointed out, we’re breathing 78% Nitrogen now. But it’s not at -300 degrees, as I was postulating. I imagine at that temperature it would have some interesting side effects, like collapsing the lungs or some other such fun. At least clearing the sinuses. ---
**Author:** ![John\_Kentzel-Griffin](https://avatars.discourse-cdn.com/v4/letter/j/ccd318/32.png) [@John\_Kentzel-Griffin](https://boards.straightdope.com/u/John_Kentzel-Griffin)\ **Post date:** [August 10, 2001, 3:37am UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/17 "2001-08-10T03:37:43Z")
\*\*Afghan \*\* I couldn’t get to your link at work, because my browser is not current enough and I can’t upgrade it. But I can get into it at home. That’s exactly what I was talking about. Thanks for the information, guys. It looks like I don’t have to worry about the thing exploding. ::whew:: ---
**Author:** ![bughunter](https://avatars.discourse-cdn.com/v4/letter/b/aeb1de/32.png) [@bughunter](https://boards.straightdope.com/u/bughunter)\ **Post date:** [August 10, 2001, 4:12am UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/18 "2001-08-10T04:12:03Z")
> [@](#): > > \*Originally posted by Chas.E \* > \*\*Due to bughunter’s question, I’m curious about the liquification points of nitrogen and oxygen. \*\* From [encyclopedia.com](http://www.encyclopedia.com/) the boiling point of Oxygen is -183.0C. The boiling point of Nitrogen is -195.8C. ---
**Author:** ![Chas.E](https://avatars.discourse-cdn.com/v4/letter/c/e99b99/32.png) [@Chas.E](https://boards.straightdope.com/u/Chas.E)\ **Post date:** [August 10, 2001, 4:33am UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/19 "2001-08-10T04:33:00Z")
Thanks, bughunter, I wasn’t aware of that site, it looks like a good replacement for [britannica.com](http://britannica.com) since they went pay. I’m always looking for new better cheaper reference sources. Oh how I wish the CRC Handbook was online. ---
**Author:** ![Chas.E](https://avatars.discourse-cdn.com/v4/letter/c/e99b99/32.png) [@Chas.E](https://boards.straightdope.com/u/Chas.E)\ **Post date:** [August 10, 2001, 4:58am UTC](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634/20 "2001-08-10T04:58:00Z")
> [@](#): > > \*Originally posted by Jargent \* > \*\*As someone pointed out, we’re breathing 78% Nitrogen now. > But it’s not at -300 degrees, as I was postulating. I imagine at that temperature it would have some interesting side effects, like collapsing the lungs or some other such fun. At least clearing the sinuses. \*\* I used to work doing computers in a hospital’s anaesthesiology lab, we did research in sensors for bottled gas respirator machines. The holy grail was a compact liquid air system but the gas it emits is too cold to work with, it takes too much energy getting it to room temperature in a controllable fashion, it’s not practical. A standard pressurized gas cylinder anaesthesiology cart uses small bottles of O2 and other anaesthetic gases (like nitrous oxide) that release gas cold enough to freeze lung tissue. Drying and burning of tissue is also a problem since the bottled gas is 0% humidity. You have to put a gas warmer and a humidifier into the system to make it breathable. And this gas is not really that cold compared to liquid gas vapor. In other words, one direct puff of liquid nitrogen vapor and your lungs would be freeze-dried. [Next page](https://boards.straightdope.com/t/liquid-nitrogen-canisters-on-sidewalk/75634.md?page=2)