People might be interested in the British Summit Oxygen systems,
originally designed for HA climbing - http://www.summitoxygen.com/index.php
.. It uses a cannula instead of a face mask and an electronic pulse-
dose meter system, which can supply up to 22 hours of oxygen from one
bottle.

Few climbers use Summit sets as they proved very unreliable on
Everest. The British Army and Navy rave about them, but that's
probably because the company was set up by two ex-Royal Engineers. Get
Mapping uses them in their aircraft, apparently.

Climbers instead use the simple but effective Russian Poisk system
that afaik has never had a failure, but requires many more bottles to
be carried. While the fancy design of the Summit system is unsuitable
for climbing, it's probably alright in the gentle environment of a
glider.


Dan