Is "medical" oxygen system suitable for part 91 aviation use?

Question

I am, in a somewhat desultory fashion, considering obtaining an oxygen system (for use in the U.S. under part 91, perhaps sharing with some passengers).

An initial search suggests that one can buy a 15 cu-ft tank with the extras (regulator, tubing, cannulas) from an aviation supplier for around USD $700

I also see that I can get a medical system for about $125 (with just a single stretch of tube, basic regulator, (but no flow-meter) and cannula).

I know that medical oxygen is sometimes disparaged for perhaps containing too much moisture, but I figure I could simply refill it with ABO anyway, right? I also read that moisture is unlikely to be present in reality today, and further that for the kind of cabin pressures I would be flying (unpressurized A/C and below 15,000' absolute maximum) this is unlikely to be an issue. But perhaps I miss something.

So... is there a compelling reason to spend the extra? Or is it likely that I have completely misread specs on things. Am I absurdly off the mark with the pricing for an aviation system (did I look at the wrong supplier, perhaps!)?

Answer 1

You are not certifying an aircraft so part 23 does not apply. Part 91 requires specific types of equipment only when flying above FL350 as follows:

91.211(b)(ii) At flight altitudes above flight level 350 unless one pilot at the controls of the airplane is wearing and using an oxygen mask that is secured and sealed and that either supplies oxygen at all times or automatically supplies oxygen whenever the cabin pressure altitude of the airplane exceeds 14,000 feet (MSL), except that the one pilot need not wear and use an oxygen mask while at or below flight level 410 if there are two pilots at the controls and each pilot has a quick-donning type of oxygen mask that can be placed on the face with one hand from the ready position within 5 seconds, supplying oxygen and properly secured and sealed.

In this one case a mask rather than a cannula is required and in one condition it must be a quick donning type.

At up to 15kft this does not apply, nor do passengers need to have oxygen by regulation. The label on the equipment is immaterial and all other references only state that when oxygen is required it shall be made "available", so your medical solution is ok with the FAA.

From a practical point of view some people get headaches as low as 10kft without oxygen, so having a provision to share might be useful although it sounds like you have been flying so far without. The "single stretch of tube and cannula" also needs a regulator and flowmeter. Oxygen is made by the way by the same companies for multiple purposes, so variation in moisture content is not an issue.

Aviation equipment costs more as the market is small. Like any product you can shop for better prices. The only step change in price that I would pay for is a pulse system, and only if I intended to use it a lot as they can cost $800 per user just for the pulsing device. These release oxygen only as you breathe in, and so conserve the amount consumed for a given saturation.