Rebreather caution...

["Alan D. Secor" <secor@btv.ibm.com>]

Just a word of caution for anyone thinking of building their own
rebreather (and if you are, you probably already know this).....
Rebreathers can be extremely dangerous...it is very easy to pass out
from hypoxia WITHOUT WARNING if there is a malfunction in the O2
delivery system.  Contrary to popular belief, it is CO2 and not O2
which triggers us to breath.  As long as the scrubber is happily
removing CO2 from the breathing loop, you'll never know what hit 
you when you pass out from hypoxia and drown.  O2 loop sensors are
used to detect this but they are not infallible especially when 
moisture is present.

The other problem is TOO MUCH O2.  If the ppO2 in the loop increases
over 1.6 ATM for an extended period of time, you run the risk of
O2 toxicity.  (Yes, O2 in high partial pressures IS toxic!)  With
O2 toxicity, you go into convulsions and pass out and drown (again
with little or no warning!)

So there you have it....the standard PSUBS safety disclaimer...
do with it what you will!

Regards........Al    

--
Alan D. Secor
e-mail: secor@btv.ibm.com