FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 9. Aircraft Systems and Components | 3. Emergency Equipment | 9-49. Maintenance
AC 43.13-1B
9/8/98
(b) The low-pressure lines extend
from the pressure regulator to each passenger
and crew oxygen outlet. These lines are fabri-
cated from seamless aluminum alloy, copper,
or flexible hose. Normally, flare- or flange-
type connections are used.
ascertain if the threaded area is free of nicks,
burrs, and contaminants that would prevent the
connections from sealing properly.
CAUTION: Do not use petroleum lu-
bricants on these components.
CAUTION: Do not allow oil, grease,
flammable solvent, or other combusti-
bles such as lint or dust to come in
contact with threads or any parts that
will be exposed to pressurized oxygen.
(c) It is advisable to purge the oxygen
system any time work has been accomplished
on any of the lines and fittings. Use dry nitro-
gen or dry air for purging the system. All open
lines should be capped immediately after
purging.
d. Masks and Hoses.
(1) Troubleshooting. If a mask assem-
bly is defective (leaks, does not allow breath-
ing, or contains a defective microphone), it is
advisable to return the mask assembly to the
manufacturer or a repair station.
(2) Maintenance Practice and Cleaning.
(a) Clean and disinfect the mask as-
semblies after use, as appropriate.
(d) When oxygen is being lost from a
system through leakage, a sequence of steps
may be necessary to locate the opening. Leak-
age may often be detected by listening for the
distinct hissing sound of escaping gas. If this
check proves negative, it will be necessary to
soap-test all lines and connections with a cas-
tile soap and water solution or specially com-
pounded leak-test material. Make the solution
thick enough to adhere to the contours of the
fittings. At the completion of the leakage test,
remove all traces of the soap and water.
CAUTION: Do not attempt to tighten
any connections while the system is
charged.
NOTE: Use care to avoid damaging
the microphone assembly while
cleaning and sterilizing.
(b) Wash the mask with a mild soap
solution and rinse it with clear water.
(c) To sterilize, swab the mask thor-
oughly with a gauze or sponge soaked in a
water merthiolate solution. This solution
should contain 1/5-teaspoon of merthiolate
per 1 quart of water. Wipe the mask with a
clean cloth and air dry.
(d) Replace the hose if it shows evi-
dence of deterioration.
c. Regulators, Valves, and Gauges. Line
maintenance of oxygen regulators, valves, and
gauges does not include major repair. These
components are precision made and their re-
pair usually requires the attention of a repair
station or the manufacturer. Care must be
taken when reinstalling these components to
(e) Hoses may be cleaned in the same
manner as the mask.
(f) Observe that each mask breathing
tube end is free of nicks, and that the tube end
will slip into the cabin oxygen receptacle with
ease and not leak.
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