I have gotten away with using EDS with

cannula up to 24,000ft or so without issues. I have had an altitude

chamber run so I can recognise the symptoms of anoxia (yes, I know it can

creep up on you).


Fixed it for you. Sorry, hot button issue. I am aware of pilots having flown the EDS/cannula system to around 27K, once or twice. That doesn't mean it's something we ought to brag about. The guy that did that has since smartened up, uses an EDS mask above 18K, has a nice constant flow backup system in place.

On constant flow, use of a mask above 18K is even more important. You probably can achieve good oxygen saturation on a constant flow cannula at 25K, but the flow rate will have to be high to do it (several liters/minute). Misleading advertising aside, a good quality rebreather mask is a far more efficient delivery device than a "pink mustache".

Evan Ludeman (Mt Wash Wave Camp Ox Nag)