> Is there a decent low oxygen sensor on the market? Does it not make
> more sense to test for the lack of something you need (oxygen) than the
> presence of something you don't?

That would indeed be better. Up until relatively recently, oxygen sensors
have been like the zirconia O2 sensors in our exhaust systems, requiring
high temperatures (meaning lots of watts from you r battery) to function;
But lately they've come up with O2 sensors that work using some method
employing a low power laser diode, so personal oxygen monitors have become
more common. I bet a personal O2 monitor could be easily mounted in the
vehicle and powered by the battery. Probably not cheap yet though. Search
around for "Oxygen Deficiency Monitor".

Wow, there's one on ebay for ten bucks! Missing its sensor element though.
How much you wanna bet that's the EXPENSIVE part...
<*http://tinyurl.com/7txzn>*

--
John Bange
'90 Vanagon - "Geldsauger"