Re: [PSUBS-MAILIST] Life Support Revisited

[William Alford <walford@dbtech.net>]

At 02:30 AM 8/2/2003 -0400, Jonathan Wallace wrote:

>Basically, I'm wondering why an 02 sensor would be necessary in a 1 ATM
vehicle as long as 02 is added as the result
>of pressure loss caused by CO2 scrubbing.

just because you have an O2 adding mechanism, how do you know it works? Perhaps
it "clicks" right along, but the line/orifice has plugged, the bottle is
mistakenly empty, the wrong gas was given to you in your tank (that's why
divers own and use them-- you can't trust you life to the "tank filler" &
people have died in hospitals because they were given the wrong gas). People
who "know better" can die from carelessness-- read this account of an
*experienced diver* who died in a home-user hyperbaric chamber because he let
his O2 supply run out and could not escape the unattended and locked chamber--
http://web.archive.org/web/20010702011808/http://www.subseaexplorer.com/info
_news_a2.asp?ID=321. Now . . . if an O2 sensor was monitoring his
atmosphere and
sounded an alarm to the attendent who had stepped away, would that not have
been a wise measly $few-hundred investment (of course there's lots of things
wrong in this sad and tragic case)? As an intellectual execise, this question
is interesting, but if you're building a sub with all the attendant bother and
cost you should be willing to invest the comparatively trivial amount to
monitor your atmosphere, just to cover all bases. There's an old tenant of
information theory, goes something like, "the importance of an event is
inversely proportional to the likelihood of occurance", kinda like those
O-rings on the space shuttle Challenger.

BTW, I understand the Hemlock Society (or some other assisted suicide group)
has described a CO2 scrubber scans O2 addition as a very humane "suicide
machine". Since the breathing reflex is driven by CO2 and not O2 lack, you
never know anything is wrong until you just lose consciousness.

William Alford