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Articles USA FAA - Pilot Safety Brochures Oxygen Equipment Use in General Aviation Operations

Oxygen Equipment Use in General Aviation Operations


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—crewmembers 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! Oxygen is highly flammable. 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 on 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).

a liquid state. The advantage of LOX is that it has a 900 to 1 expansion ratio. In other

words, one liter of LOX will expand into 900 gaseous liters of ABO. This will afford a

3 to 1 space and a 5 to 1 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 come in contact with petroleum products. If LOX comes in contact with

exposed skin,

Oxygen can be serviced to the aircraft insevere frostbite may occur.

Sodium chlorate candles (solid-state


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

it provides a 600 to 1 expansion ratio.

The major disadvantage is that once the chemical reaction (the candle is activated) has

started, it can’t be easily stopped. Additionally, the candle produces a great deal of heat,

and precautions must be taken to avoid a fire hazard.

Sodium chlorate is a chemical

Molecular sieve oxygen generators (MSOG).

21% oxygen, and the remainder is inert gases that play no major physiological role in

the body. MSOGs take ambient air and separates oxygen from inert gases, using that to

supply oxygen to 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 be more in vogue in future aircraft.

The air that we breathe contains basically

Oxygen Delivery Systems

Continuous flow.

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 flow of oxygen is constant

whether you’re inhaling, exhaling, or pausing in between breaths. This system is typically

used at 28,000 feet and lower.

This system delivers a continuous flow of oxygen from the storage

Diluter demand.

to compensate for the short-comings of the continuousflow

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.

The diluter demand system is designed

Pressure demand.

positive pressure. Positive pressure is a forceful oxygen

flow that is intended to slightly over-inflate 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 will not suffice.

This system provides oxygen under

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.

the advantage of personal comfort. They are restricted by

federal aviation regulations to 18,000 feet service altitude

because of the risk of reducing oxygen-blood saturation levels

if one breathes through the mouth or talks too much.

These are continuous-flow devices and offer

Oral-nasal re-breather.

the most common and least expensive. It is also the simplest in

operation; it has an external plastic bag that inflates every time you

exhale. The purpose of the bag is to store exhaled air, so 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


This type is

Quick-don mask.

demonstrate the ability 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 cockpit crew. These masks are

typically rated to altitudes up to 40,000 feet.

These masks must

Airline drop-down units (Dixie cup).

continuous-flow mask looks similar to a general aviation rebreather.

However, both masks function differently, and the phase

sequential mask allows the user to go to higher altitudes. This mask

uses a series of one-way ports that allow a mixture of 100% oxygen

and cabin air into the mask. Exhalation is vented to the atmosphere;

as a result, the bag does not inflate. This mask can be safely used at

emergency altitudes up to 40,000 feet.

The phase-sequential

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 that helps 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, make sure 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

assure 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 those

emergencies that call for oxygen (hypoxia, decompression sickness, smoke and

fumes, and rapid decompressions.) This step should include briefing passengers

on the location of oxygen and its proper use.


To get first-hand experience using oxygen equipment, it is highly recommend

that all pilots, especially those operating their aircraft at altitudes where oxygen

is required, get additional training in an altitude chamber. The Federal Aviation

Administration offers several of these valuable training programs through the U.S.

Air Force and Army. If interested, use the contact information at the end of this



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.

Federal Aviation Regulations and Oxygen Use

(Title 14 of the Code of Federal Regulations)

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


Commuter and On Demand Operations and Rules

Governing Persons On Board Such Aircraft

§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

(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 crewmember’s station.




Publication OK-08-639

Written by: J.R. Brown, A. Salamanca, MD

Prepared by:

Federal Aviation Administration

Civil Aerospace Medical Institute

Aerospace Medical Education Division

P.O. Box 25082

Oklahoma City, OK 73125

To order copies of this brochure,

write to the above address.

Physiological Training Classes for Pilots

If you are interested in taking a one-day aviation physiological training course with

altitude chamber and vertigo demonstrations or a one-day survival course, learn about

how to sign up for these courses that are offered at various locations across the U.S. by

visiting this FAA Web site:

For more pilot and traveler safety

information, see:



This article was published by Federal Aviation Administration. Please visit for current information - Reprinted with permission.

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