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From: jenkins@jpl-devvax.JPL.NASA.GOV (Steve Jenkins)
Newsgroups: sci.space.shuttle
Subject: Re: What happened?  Could risk be higher?
Message-ID: <6595@jpl-devvax.JPL.NASA.GOV>
Date: 14 Dec 89 17:08:19 GMT
References: <4014@samoa.cs.glasgow.ac.uk>
Reply-To: jenkins@jpl-devvax.JPL.NASA.GOV (Steve Jenkins)
Organization: Jet Propulsion Laboratory, Pasadena, CA
Lines: 16

In article <4014@samoa.cs.glasgow.ac.uk> willisa@cs.glasgow.ac.uk (Mark Willis) writes:
>Asking how long can a person stay conscious in a total vacuum is similar
>to asking how long can a person hold his breath for, which is at least a
>minute, and probably a lot longer in a vacuum because you can't cheat.

It's nothing like holding your breath.

In particular, you can't oxygenate blood in a vacuum.  Unless you're
holding your breath already (and manage to exhale enough to avoid
damaging your lungs at precisely the right moment), your arterial PO2
will drop below the threshold of consciousness well within 30 s.
(Not to mention the risk of embolism.)

-- 
Steve Jenkins      			jenkins@jpl-devvax.jpl.nasa.gov
Caltech/Jet Propulsion Laboratory	(818) 354-0162