Hacker News Reader

Comment by yomly | Hacker News Reader

What kinds of safety risks are there in storing liquid nitrogen in a DIY context? If your container is well sealed and sufficiently strong (define sufficiently...) can you store it in a room temperature garage?

What happens if it's a freakishly hot summer one year? Do you have a ticking time bomb in your garage?

View on HN

I’ve never seen a fully sealed LN2 tank. Granted I’ve only worked with the ones for university labs, but all of them have a pressure release valve that’s goes off periodically, with a secondary back up valve.

Is this what you consider sealed? If not, you’ll most likely be creating a bomb.

Okay I’ve read a story about a fully sealed tank: https://corante.com/how-not-to-do-it/how-not-to-do-it-liquid...

>can you store it in a room temperature garage?

I'm from texas, and that's just a strange use of words in a sentence to read. The air temp outside is 95+ (in the shade) this time of year, and lately >50% humidity. It's stifling hot. Step into the garage, and it is even hotter. Most garages have zero air flow, and rarely are they insulated. It's the least friendly "room" of my house.

>What happens if it's a freakishly hot summer one year?

We call that a Tuesday.

There is no danger in storing LN in your garage. Your container won't be tightly sealed (a tightly sealed container full of LN likely is a bomb); gaseous LN will continually leak from your dewar. It's nitrogen, who cares?

The major risk with LN is storing it in enclosed spaces, as it can quickly asphyxiate you. So, like, don't take it in an elevator.

I'm not sure I understand what the ambient temperature has to do with LN safety.

Actually can't leaking N2 cause asphyxiation via air displacement?

A large spill is what you're worried about. The container has to leak, so as not to, you know, explode. It's worth keeping the asphyxiation risk in mind, but you're probably overthinking this; people keep large dewars in tiny restaurant kitchens.

There can be danger in improperly storing LN if it comes into contact with air, since it will liquefy oxygen. Liquid O2 is a very dangerous thing to have in your garage.

Huh, interesting. How would that work with dewar, though? The LN is constantly evaporating and pushing gas out of the container.

The garage thing seems like a good point, because, yeah, if there's one place in the world you don't accidentally want to collect liquid oxygen... (goes to move dewar).

The typical situation where this happens in a chem lab (where I learned about this stuff) is having glass tubing immersed in a dewar as a vapor trap for a vacuum pump. In normal operation, the tubing has near-vacuum inside, and the liquid nitrogen condenses any volatiles that might get into the vacuum system.

But if you open the vacuum system to the air and leave it immersed in the dewar, then you can condense a considerable amount of oxygen in the bottom of the vapor trap... which is already covered in whatever organic gunk you were trapping in the first place.

I post this not because I think people keeping a thermos of liquid N2 in their garage need to worry about it, but because it's such a nonobvious way to blow yourself up with what is in all other respects a docile substance.

Is your garage actively ventilated? Mine (in my previous house, I live in an apartment now) was a closed room with a pulldown door (always closed) and a window that didn't open. It's not hermetically sealed, but how confident are you it wouldn't become saturated with N2 gas?

>If your container is well sealed and sufficiently strong

Trying to contain it in a strong sealed container is a very very bad idea. That's a bomb, even if it's freezing out.

You store it in dewers that allow it to slowly boil off, and replenish it as needed.

You should also ventilate the area if storing or working with a considerable amount. Even a few litres boiling could displace enough air in a small room that asphyxation is a real risk.

You don't want it to be completely sealed, because it will eventually warm up and boil. If it does so in a sealed container, PV=nRT implies that your container will either need to expand dramatically or handle a lot of pressure. This can be....unexpectedly invigorating, especially if the container is strong.

Instead, it's common to have a pressure-relief valve, often coupled with a gas sensor to make sure everything remains safe.

I would be more worried about asphyxiation due to accidental release.

This is why a garage-type situation would probably be better. At least in my garage there's a not-great enough seal that any leaks would go outside before they'd go in the house.

Reply on news.ycombinator.com