Posted by Frank Farmer on September 18, 2000 at 22:01:37:
In Reply to: Secondary Air source question posted by JRM on September 13, 2000 at 08:38:06:
I wreck dive exclusively with a 120 cu ft 3500 psi steel main and a 30 or 40 cu ft aluminum 3000 psi pony. I have 21% air in my main and 40% O2 (EANx) in my ponies. I restrict my depth to 110 feet or less. I dive the main down to 500 psi then switch to the pony for ascent, using a NiTek3 computer with a Suunto back up.
SpareAir was originally intended as a bail out bottle for helicopter pilots. To my knowledge it's never been tested for panic ascent breathing, in which case it would hardly provide enough air to reach the surface from average diving depths. You're right about costs, so dollar for dollar I'd rather pack too much gas than not enough.