or any other approved cleaner. If mask-to-regulator hoses are contaminated with oil or grease, the hoses should be replaced.
Cleaning Compound, Oxygen System An approved cleaning formula for use on oxygen systems is available. This mixture of chlorinated, fluorinated hydrocarbons (freon) and isopropyl alcohol is safe for cleaning oxygen system components in aircraft, and for rinsing, flushing, and cleaning oxygen lines. Skin contact and prolonged inhalation of vapors should be avoided.
Purging the Oxygen System An oxygen system needs to be purged if: (1) It has been depleted and not re-charged within 2 hrs.,
(2) if any line or component is replaced, requiring the draining or opening of the system for more than 2 hrs., or (3) it is suspected that the system has been contaminated.
The main cause of contamination in the system is moisture. Moisture in the system may be due to damp charging equipment. In very cold weather the small amount of moisture contained in breathing oxygen can cause contamination, due to repeated Although the introduction of moisture into the aircraft oxygen system can be considerably reduced by using the correct charging procedure, cumulative condensation in the system cannot be entirely avoided. There have been instances where oxygen systems, unused for long periods, have developed an unpleasant odor which necessitated purging to clear the system of moisture.
The procedure for purging may vary somewhat with each aircraft model. Generally speaking, on aircraft having the filler lines and the distribution lines commonly connected to one end of the storage cylinder, the system can be purged by filling the system with oxygen and then draining it at least three times. On aircraft that have the filler lines connected on one end of the cylinder and distribution lines connected to the opposite end of the cylinder, purge the system as follows: With all the regulator emergency palves open, pass oxygen at a pressure of 50 p.s.i. at the filler valve through the system for at least 30 min. Perform this job in a well-ventilated area and observe all fire precautions.
Dry nitrogen and/or dry air may also be used to purge oxygen systems. All open lines must be capped after use, also the system lines must be purged of the nitrogen by use of oxygen.
PREVENTION OF OXYGEN FIRES OR EXPLO SIONS Many materials, particularly oils, grease, and non-metallic materials, are likely to burn when exposed to oxygen under pressure. To avoid fire or an explosion it is essential that all oxygen equipment be kept clean and free from oil or grease.
An oxygen fire or explosion depends on a combination of oxygen, a combustible material, and heat.
The danger of ignition is in direct ratio to the concentration of oxygen, the combustible nature of the material exposed to the oxygen, and the temperature of the oxygen and material. Oxygen itself does not burn but it supports and intensifies a fire with any combustible material.
When working on an oxygen system it is essential that the warnings and precautions given in the aircraft maintenance manual be carefully observed. In general, before any work is attempted on an oxygen system the following fire precautions should be taken:
(1) Provide adequate fire-fighting equipment.
(2) Display "NO SMOKING" placards.
(3) Avoid checking aircraft radio or electrical systems.
(4) Keep all tools and oxygen servicing equipment free from oil or grease.
Oxygen System Inspection and Maintenance Oxygen system inspection and maintenance should be accomplished according to these precautionary measures and any in addition to the manufacturer's instructions.
1. Never attempt maintenance until oxygen supply is turned off.
2. Fittings should be unscrewed slowly to allow residual pressure to dissipate.
3. Plug or cap all open lines immediately.
4. Do not use masking tape to seal openings:
use caps or plugs designed for that purpose.
5. Maintain at least 2 inches clearance between oxygen lines and all moving equipment/ parts within the aircraft to prevent the possibility of wearing oxygen lines.
6. Maintain at least 2 inches clearance between oxygen lines and all electrical wiring in the aircraft.
7. Provide adequate clearance between oxygen lines and all hot ducts, conduits and equip- 600
ment to prevent heating of the oxygen system.
8. Maintain at least 2 inches clearance between oxygen lines and all oil, fuel, hydraulic, or other fluid lines to prevent contamination.
* U.S. G.P.O.: 1996-873-S/20104 601
9. Do not use lubricants unless specifically approved for oxygen system use.
10. A pressure and leak check must be performed each time the system is opened for maintenance.