Oxygen Equipment Use in
General Aviation Operations
A basic knowledge of oxygen equipment can be critical
whether you are flying a commercial, commuter, or a
general aviation aircraft. This equipment is the first line
of defense against the potentially lethal effects of hypoxia
and carbon monoxide poisoning. It is the responsibility of
the pilot that all aboard the aircraft, crew-members and
passengers, know how to use this life-saving equipment
safely and efficiently.
General Precautions
This pamphlet describes operational precautions to use
with all types of oxygen systems. The basic principles and
practices include:
• Keep your equipment clean. The interaction of
oil-based products and oxygen creates a fire hazard.
Additionally, oil attracts dirt particles, and these dirt
particles can contaminate storage containers,
regulators, masks, and valves. For cleaning
instructions, check with the manufacturer’ s guide.
• Protect your oxygen mask from direct
sunlight and dust. Store in proper containers.
• Inspect oxygen storage containers. Make sure that
they are securely fastened in the aircraft, as turbulence
or abrupt changes in attitude can cause them to come
loose. Proper inspections are important, so your oxygen
equipment should be inspected regularly at an
authorized Federal Aviation Administration
inspection station.
• No smoking! Although oxygen itself is not flammable,
it can cause other materials to ignite more easily and
will make existing fires burn hotter and faster. Do not
allow anyone to smoke around oxygen equipment that
is being used. Likewise, no one should smoke around
oxygen equipment that is being recharged. Ensure that
the aircraft is properly grounded before loading oxygen.
• Mix and match components with caution. When
inter-changing oxygen systems components, ensure
compatibility of the components - storage containers,
regulators, and masks.
Basic Components
There are three components to most oxygen systems,
whether they are portable or installed systems.
• A storage system (containers)
• A delivery system
• Mask or nasal cannula
Storage Systems
Oxygen can be stored in the aircraft as a gas, liquid,
or a solid.
Gaseous aviator’s breathing oxygen (ABO). Storing
oxygen as a gas has the major advantage of being more
economical. It can be stored in high-pressure (1800-2200
psi) containers or low-pressure (400-450 psi) containers.
The major disadvantage is the weight and bulk of the
storage containers, which may become an issue in smaller
aircraft. Aviator’s oxygen must meet certain standards to
ensure that it is safe to be taken to altitude. Only aviator’s-
grade breathing oxygen meets this specification. Neither
medical grade nor
industrial grade
oxygen is safe to
substitute because
they do not meet the
same stringent standards as ABO.
Liquid aviators breathing oxygen (LOX). Oxygen can
be serviced to the aircraft in a liquid state. The advantage
of LOX is that it has a nine hundred-to-one expansion
ratio. In other words, one liter of LOX will expand into 900
gaseous liters of ABO. This provides a three-to-one space
and a five-to-one weight savings over gaseous ABO. The
major disadvantages are that LOX is stored at its critical
temperature of minus 197º F and its volatile nature when it
comes in contact with petroleum products. If LOX comes in
contact with exposed skin, severe frostbite may occur.
Sodium chlorate candles (solid-state oxygen). Sodium
chlorate is a chemical that, when heated to 350º F, will
thermally decompose and release oxygen. Sodium chlorate
candles have the
advantage of saving
weight and space
over ABO because
they provide a six hundred-to-one expansion ratio. The
major disadvantage is that once the chemical reaction
starts (the candle is activated), it can’t be stopped easily.
Additionally, the candle produces a great deal of heat and
precautions must be taken to avoid a fire hazard.
Molecular sieve oxygen generators (MSOG). The air
we breathe contains 21% oxygen and the remainder
is nitrogen and inert gases that play no major role in
respiration. MSOGs take ambient air and separate oxygen
from the nitrogen and inert gases. The separated oxygen is
concentrated and used to supply the aircraft. . The military
has used this system for many years, as well as medical
patients who need a portable oxygen system. Civil aviation
hasn’t embraced MSOG, but it may become more common
in future aircraft.
Oxygen Delivery Systems
Continuous flow. This system delivers a continuous flow of
oxygen from the storage container. It is a very economical
system in that it doesn’t need complicated masks or
regulators to function. But it is also very wasteful—the
oxygen flow is constant whether you’re inhaling, exhaling,
or pausing in between breaths. This system is typically
used at 28,000 feet and lower.
Diluter demand. The diluter
demand system is designed
to compensate for the short-
comings of the continuous-
flow system. It gives the
user oxygen on-demand
(during inhalation) and stops
the flow when the demand
ceases (during exhalation).
This helps conserve oxygen.
Additionally, the incoming oxygen is diluted with cabin air
and provides the proper percentage of oxygen, depending
on the altitude. This system is typically used at altitudes up
to 40,000 feet.
Pressure demand. This
system provides oxygen
under positive pressure.
Positive pressure is a
forceful oxygen flow that
slightly over-inflates the
lungs. This will, in a sense, pressurize the lungs to a lower
altitude, thus allowing you to fly at altitudes above 40,000
feet, where 100% oxygen without positive pressure is
insufficient.
Oxygen Masks and Cannulas
When considering an oxygen mask, you must ensure that
the mask you are using is compatible with the delivery
system you are using.
Nasal cannulas. These are
continuous-flow devices
and offer the advantage of
personal comfort. They are
restricted by federal aviation
regulations to 18,000 feet
service altitude because of
the risk of reducing blood
oxygen saturation levels if one breathes through the mouth
or talks too much.
Oral-nasal re-breather. This
mask is the most common
and the least expensive. It
is also the simplest to use;
; it has an external plastic
rebreather bag that inflates
every time you exhale. The
purpose of the rebreather bag
is to store exhaled air, so that
it may be mixed with 100%
oxygen from the system.
These masks supply adequate oxygen to keep the user
physiologically safe up to 25,000 feet.
Quick-don mask. These
masks must have the capability
to be donned with one hand
in 5 seconds or less, while
accommodating prescription
glasses. Quick-don masks are
typically suspended or stored
to permit quick and unimpeded
access by flight deck crew. These
masks are typically rated to
altitudes up to 40,000 feet.
Airline drop-down
units (Dixie cup).
The continuous flow,
phase-dilution (or
phase-sequential)
mask looks similar
to a general aviation
re-breather mask.
However, the masks
function differently and
the phase dilution mask
allows the user to go
to higher altitudes. This
mask uses an external reservoir bag and a series of one-
valves working in sequence to allow a mixture of 100%
oxygen and cabin air into the mask. When activated by
pulling down on a suspended mask, oxygen from a supply
source flows continuously into the reservoir bag. During
inhalation, a one-way valve allows the flow of oxygen
from the reservoir bag into the lungs. If the reservoir bag
empties before inhalation is complete, a second one-way
valve on the mask face piece opens to permit the flow of
cabin air into the mask, allowing the user to take a full
breath. If the user is breathing rapidly the reservoir bag
will appear to not fully inflate. Expired air is vented out of
the mask into the cabin via a one-way exhalation valve;
expired air is not returned to the reservoir bag.
This mask can be safely used at emergency altitudes up to
40,000 feet.
The PRICE Check
Prior to every flight, the pilot should perform the “PRICE”
check on the oxygen equipment. The acronym PRICE is a
checklist memory-jogger to help pilots and crewmembers
inspect oxygen equipment.
• PRESSURE. ensure that there is enough oxygen
pressure and quantity to complete the flight.
• REGULATOR. inspect the oxygen regulator for proper
function. If you are using a continuous-flow system,
ensure that the outlet assembly and plug-in coupling
are compatible.
• INDICATOR. most oxygen delivery systems indicate
oxygen flow by use of flow indicators. Flow indicators
may be located on the regulator or within the oxygen
delivery tube. Don the mask and check the flow
indicator to ensure a steady flow of oxygen.
• CONNECTIONS. ensure that all connections are
secured. This includes oxygen lines, plug-in coupling,
and the mask.
• EMERGENCY. have oxygen equipment in the aircraft
ready to use for emergencies that require oxygen
(hypoxia, smoke and fumes, rapid decompressions/
decompression sickness). This step should inc lude
briefing passengers on the location of oxygen and its
proper use.
Be Aware
From a safety-of-flight standpoint, oxygen equipment is an
issue that should concern all pilots. Know the equipment
you have on board, know when to use it, and most
importantly, know its limitations. It’s your key to a safe and
enjoyable flight.
§91.211 Supplemental oxygen.
(a) General. No person may operate a civil aircraft of U.S. registry—
1) At cabin pressure altitudes above 12,500 feet (MSL) up to and
including 14,000 feet (MSL) unless the required minimum flight
crew is provided with and uses supplemental oxygen for that part
of the flight at those altitudes that is of more than 30 minutes
duration;
(2) At cabin pressure altitudes above 14,000 feet (MSL) unless
the required minimum flight crew is provided with and uses
supplemental oxygen during the entire flight time at those altitudes;
and
(3) At cabin pressure altitudes above 15,000 feet (MSL) unless each
occupant of the aircraft is provided with supplemental oxygen.
(b) Pressurized cabin aircraft. (1) No person may operate a civil
aircraft of U.S. registry with a pressurized cabin—
(i) At flight altitudes above flight level 250 unless at least a
10-minute supply of supplemental oxygen, in addition to any
oxygen required to satisfy paragraph (a) of this section, is available
for each occupant of the aircraft for use in the event that a descent is
necessitated by loss of cabin pressurization; and
Federal Aviation Regulations and Oxygen Use
(Title 14 of the Code of Federal Regulations)
PART 91
GENERAL OPERATING AND FLIGHT RULES
(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.
(2) Notwithstanding paragraph (b)(1)(ii) of this section, if for any
reason at any time it is necessary for one pilot to leave the controls
of the aircraft when operating at flight altitudes above flight level
350, the remaining pilot at the controls shall put on and use an
oxygen mask until the other pilot has returned to that crew-
member’s station.
Sec. 135.89 Pilot requirements: Use of Oxygen.
(a) Unpressurized aircraft. Each pilot of an unpressurized aircraft
shall use oxygen continuously when flying—
(1) At altitudes above 10,000 feet through 12,000 feet MSL for
that part of the flight at those altitudes that is of more than 30
minutes duration; and
(2) Above 12,000 feet MSL. (b) Pressurized aircraft. (1) Whenever
a pressurized aircraft is operated with the cabin pressure altitude
more than 10,000 feet MSL, each pilot shall comply with
paragraph (a) of this section.
(2) Whenever a pressurized aircraft is operated at altitudes above
25,000 feet through 35,000 feet MSL, unless each pilot has an
approved quick-donning type oxygen mask–
(i) At least one pilot at the controls shall wear, secured and
sealed, an oxygen mask that either supplies oxygen at all times or
automatically supplies oxygen whenever the cabin pressure altitude
exceeds 12,000 feet MSL; and
(ii) During that flight, each other pilot on flight deck duty shall
have an oxygen mask, connected to an oxygen supply, located so
as to allow immediate placing of the mask on the pilot’s face sealed
and secured for use.
(3) Whenever a pressurized aircraft is operated at altitudes above
35,000 feet MSL, at least one pilot at the controls shall wear,
secured and sealed, an oxygen mask required by paragraph(b)(2)(i)
of this section.
(4) If one pilot leaves a pilot duty station of an aircraft when
operating at altitudes above 25,000 feet MSL, the remaining pilot
at the controls shall put on and use an approved oxygen mask until
the other pilot returns to the pilot duty station of the aircraft.
PART 135
OPERATING REQUIREMENTS:
Commuter and On Demand Operations and Rules
Governing Persons On Board Such Aircraft
Physiological Training Classes for Pilots
CAMI offers physiological training for civil aviation pilots,
FAA flight crews, and FAA aviation medical examiners
at our facilities in Oklahoma City, Oklahoma including
practical demonstrations of rapid decompression in a
hypobaric (altitude) chamber or Portable Reduced Oxygen
Training Enclosure (PROTE). Visit this FAA website to sign
up for this training: https://faa.gov/go/aerophys
Provided by
Aerospace Medical Education Division, AAM-400
To obtain copies of this brochure online:
http://www.faa.gov/pilots/safety/pilotsafetybrochures/
or contact:
Federal Aviation Administration
Aviation Safety
Civil Aerospace Medical Institute
AAM-400
P .O. Box 25082
Oklahoma City, OK 73125
(405) 954-4831
OK-21-0375 12/28/2021