You're breathing 78% nitrogen right now

(moon monkey is busy making memories worth repressing, Tue 20 Sep 2011, 15:35, 2 replies)

Yup, indeed we are.
However it wouldn't take much effort or poor ventilation to bollocks that % right up.
The ventilation's the thing.
( blaireau69 , the Cumbrian Travis Bickle., Tue 20 Sep 2011, 15:37, closed)

ooh, I'd never have know that. Cheers for the info.
200L of liquid nitrogen is 200 cubic metres of gas, more or less. That's enough to completely displace all the air in a fairly large room. And you pass out at around 12% oxygen and you die around 8-10%, so you'd only need to displace just over half of it to kill everyone.

To put it into context, knocking over a dewar (liquid content a couple of litres) can and has proved fatal in small enough research labs, particularly basement ones. Which is why all mine have low 02 alarms. 200 L in a day? not unless it was in a hangar.
( the mighty badger Aphrodite, on a bar stool, by your side, Tue 20 Sep 2011, 15:46, closed)

Seeing as you seem to know about this sort of thing...
How much would 2,000 litres of liquid nitrogen set one back?
( blaireau69 , the Cumbrian Travis Bickle., Tue 20 Sep 2011, 15:49, closed)

I dunno, invoices for filling my dewars go to a different Uni department
for some obscure reason. It's not expensive, though. Cost certainly isn't the restraining factor in the likelihood of the above story being true.
( the mighty badger Aphrodite, on a bar stool, by your side, Tue 20 Sep 2011, 15:52, closed)

Since you're interested
I just called my facilities manager. BOC charge around 30 pence a litre for liquid N2. Although there's a fairly sizable minimum order.
( the mighty badger Aphrodite, on a bar stool, by your side, Tue 20 Sep 2011, 15:55, closed)

It's cheap because it's a waste product. The boiling point of nitrogen is fairly high as far as cryogenics go, where all the rare expensive gases such as argon are much lower. They basically obtain shit loads of liquid nitrogen in the pursuit of obtaining the rarer gases from air which they sell at a massive premium.

Hence LN2 is as cheap as frozen chips. But the storage cylinders aren't cheap. They are stainless pressure vessels that vent in order to keep a low temperature.

But 200L is about 140 cubic metres of gas at ambient conditions and sounds like a supiciously dangerous way to air condition an office. With nitrogen asphyixiation you don't get any warning, you just pass out and die.

He might have got away with it if it's a large well ventilated office with no midgets working in it.
( Draconacticus Reject shampoo. Demand real poo!, Tue 20 Sep 2011, 16:02, closed)

yeah, I know, I've bought a few dewars in my time.
I don't use the stuff in large quantities though, top-ups to the dewars with my cell banks in once a week really.
( the mighty badger Aphrodite, on a bar stool, by your side, Tue 20 Sep 2011, 16:09, closed)

We used it in an experiment in power generation from it. We had a 950 litre high pressure dewar with a 4kW ambient evaporator attached to it and ran the nitrogen through an expander to generate power.

We vented the nitrogen outside because it's an asphyxiant despite the apparent air conditioning advantages. But we still managed to fill a huge warehouse with an eerie 2 foot deep fog that formed from air passing over the evaporator.

Fun day that :)
( Draconacticus Reject shampoo. Demand real poo!, Tue 20 Sep 2011, 16:14, closed)

Not all at once.
If it had been done, the 200l would have been pumped out over seven or eight hours.
(ubergeekian, Tue 20 Sep 2011, 23:04, closed)