AOPA Pilot Magazine - December 2023 - 22

FLIGHT MD
Oxygen is oxygen
Use it so you don't lose it
BY DR. BRENT BLUE
OXYGEN IS OXYGEN IS OXYGEN. There is a lot of misinformation
out there about medical oxygen versus aviator breathing oxygen
versus industrial-grade welding oxygen, but the bottom line is
that is all three are the same.
When oxygen was being produced from various sources 50
or more years ago, there were different methods of dispensing it.
For instance, medical oxygen had water added to it to humidify
it. This caused problems, including rust in steel tanks. Adding
water has not been done for more than 30 years. Now medical
oxygen, when needed, is humidified at the bedside through a
simple plastic bubble device containing water.
As you might guess, the idea of water in oxygen scared the
aviation regulators since there was great concern about this
vapor freezing in oxygen lines when aircraft were at high, cold
altitudes. In response to this concern, aviator breathing oxygen
(ABO) standards were developed by the FAA in the 1950s. These
standards required oxygen suppliers to certify their oxygen
was " dry " by requiring several tests for water vapor. The only
difference between ABO and other oxygen types is the testing.
I am a big believer in using supplemental oxygen.
As I have said in previous columns, the 12.5/14
FAA rule for oxygen use is antiquated. Oxygen need
should be an individual-based requirement. Some
people need oxygen at much lower altitudes.
All oxygen for the past 30 or so years for all purposes
supplied to aviation, medical, or welding users comes from
liquid oxygen sources. Because of the extreme cold nature of
liquid oxygen (about minus 300 degrees Fahrenheit), no water
exists in liquid form and, if present, does not enter the system
for filling gas cylinders.
For certified aircraft, the FAA requires oxygen fills to be done
with ABO. However, I know there are many folks who fill their
own aircraft using a two- or three-H cylinder cascade system
with valves and gauges obtained through gas companies or
online. This oxygen can be obtained from most gas suppliers. By
22
AOPA PILOT / December 2023
the way, some welding oxygen is more pure than standard oxygen
since it is used for very specialized welding such as spacecraft,
which cannot have any impurities.
Portable oxygen systems can be filled with oxygen at
regular gas or medical suppliers. Portable systems may be made
specifically for aviation use, but regular portable medical systems
work fine for most flights under Part 91. Portable medical systems
are far less expensive than those sold by aviation suppliers. Some
gas suppliers require a prescription even though the need is
for aviation, not medical use. Prescriptions for oxygen can be
obtained from your local physician; if you have any trouble, reach
out to me by email.
Oxygen, for the most part, is inexpensive. However, time
duration of the supply is the critical issue for most pilots. There
are several ways to increase a system's duration.
Older built-in systems are set to deliver oxygen flow rate for
the certified ceiling of the aircraft. If you are at 15,000 feet msl
and your aircraft is certified to 25,000 feet you will be getting
2.5 liters per minute of oxygen. This is based on antiquated
FAA regulations which set flow at one liter per minute for
each 10,000 feet above msl. Adding a flow regulator and using
a pulse oximeter to adjust the flow can extend oxygen duration
significantly. Adding a conserving cannula (like the Oxymizer)
will also increase the duration. (Some newer aircraft and a few
older ones have altitude compensating regulators which adjust
flow for altitude.)
I am a big believer in using supplemental oxygen. As I have
said in previous columns, the 12.5/14 FAA rule for oxygen use
is antiquated. Oxygen need should be an individual-based
requirement. Some people need oxygen at much lower altitudes,
especially at night or on long trips.
The FAA is not inclined to change any oxygen regulations
since there is no lobby or other pressure to go through the cumbersome
process. This is unfortunate but should not stop pilots
from using modern
information and modern
devices like pulse oximeters
to judge their oxygen
requirements.
brent@brentblue.com
DR. BRENT BLUE is a senior
AME who flies out of and
sees patients at Driggs-Reed
Memorial Airport (DIJ) near
Jackson Hole.
AOPA Pilot Magazine - December 2023

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