RE: Liquid Nitrogen - Oxygen depletion

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From:Alan Bright <>,
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Dear Richard,

I know this does not answer your question, but we manufacture an ultra
low -80 degs.C specimen freezer for specimen fast freezing prior to
sectioning named 'Clini-RF' this is mainly used to eliminate the need for
Liquid Nitrogen & carbon dioxide and the associated hazards you mention.
Brief details can be viewed on our website

Best Regards

Alan Bright

Bright Instrument Co.Ltd.
St Margaret's Way
PE18 6EB

Tel No:+44 (0)1480 454528
Fax No:+44 (0)1480 456031
Web Site:

-----Original Message-----
Sent: 09 March 2000 09:22
Subject: Liquid Nitrogen - Oxygen depletion

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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