Liquid Nitrogen - Oxygen depletion

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Hi All,

We have stored tissues in liquid nitrogen for many years. We have two 35 litre dewars actually in the lab, replenished from a 250 litre store located outside the department. The hospitals Occ Health and Safety dept. have received a mail shot from a company which supplies oxygen depletion monitors. We both agree that we should install one of these gadgets in the lab, even though we've had no problems to date.

(We did once have a vacuum failure in one of the Dewars, and 35 litres of N2 boiled off. Luckily, our lab is well ventilated (draughty).)

Does anyone else have experience of these monitors -  are they a legal requirement in some areas ?

Anyone know how many cubic metres of N2 gas  is evolved from 1 litre of liquid ?

The reasoning is that N2 displaces oxygen, thus entry to a room with a faulty N2 store could have fatal consequences - I have a vague recollection that this happened recently in a lab in Scotland, any info on this ?

Richard Pitman FIBMS,
Head MLSO,
Dept of Histology, Cytology & Immunology,
Worcester Royal Infirmary NHS Trust

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