and clearly, when called, require immediate
BETWEEN 25,000 AND 30,000 FEET.
Between 25,000 and 30,000 feet, collapse,
unconsciousnes, and death quickly follow
interruption of the oxygen supply. Mask leakage
at these altitudes may cause a degree of hypoxia
that, although not noticed during flight, can
produce considerable fatigue and have serious
ABOVE 30,000 FEET. Above 30,000 feet,
unconsciousness and death strike rapidly and
often without warning. At such altitudes,
it is imperative that all oxygen equipment be
functioning correctly and that each breath be
taken through a properly fitted oxygen mask.
Above a pressure altitude of 35,000 feet, pressure
breathing oxygen equipment is required.
GASEOUS OXYGEN SYSTEMS
Learning Objective: Identify safety pre-
cautions, components, typical systems, and
maintenance procedures for gaseous
Gaseous oxygen systems are used primarily in
large, multiplace aircraft where space and weight
limitations are less important items and the
systems are used only periodically.
The pressure in gaseous oxygen supply
cylinders should not be allowed to fall below 50
psi. If the pressure falls much below this value,
moisture is likely to accumulate in the cylinder
and could be introduced into the oxygen system
of the aircraft, causing component malfunction.
All oxygen under pressure is potentially very
dangerous if handled carelessly. Personnel
servicing or maintaining oxygen systems and
components must be meticulously careful about
preventing grease, oil, hydraulic fluid, or similar
hydrocarbons as well as other contamination from
coming in contact with lines, hoses, fittings, and
equipment as this contact presents a fire and
If, because of hydraulic leaks or some other
unpreventable malfunction, components of
the oxygen system do become externally con-
taminated, they should be cleaned using only
approved oxygen system cleaning compounds.
While some MIMs specify the use of a variety of
cleaning compounds, the preferred compound is
oxygen system cleaning compound conforming to
Military Specification MIL-C-8638 or ultra clean
solvent cleaning compound (type I, trichlorotri-
fluoroethane) conforming to Military Specifica-
The following safety precautions should be
l Under no circumstances should a non-
approved cleaning compound be used on any
oxygen lines, fittings, or components.
. When handling oxygen cylinders, the valve
protection cap should always be in place. Before
removing the cap and opening the valve, ensure
that the cylinder is firmly supported. A broken
valve may cause a pressurized cylinder to be
propelled like a rocket.
. Do NOT use oxygen in systems intended
for other gases or as a substitute for compressed
. Cylinders being stored for use on gaseous
oxygen servicing trailers or any other use must
always be properly secured. Do not handle
cylinders or any other oxygen equipment with
greasy hands, gloves, or other greasy materials.
The storage area should be located so that
oil or grease from other equipment cannot be
accidentally splashed or spilled on the cylinders.
Additional safety precautions may be
found in the publications technical manual
NAVAIROSH Requirements for the Shore
Establishment, NAVAIR A1-NAOSH-SAF-000/
P-5100; Aviators Breathing Oxygen (ABO)
Surveillance Program Laboratory Manual and
Field Guide, A6-332A0-GYD-000; Aviation-Crew
System, Oxygen Equipment, NAVAIR 13-1-6.4.
Basically, all gaseous oxygen systems consist
of the following:
Containers (cylinders) for storing the
Tubing to route the oxygen from the main
supply to the user(s)
Various valves for directing the oxygen
through the proper tubing