diaphragm (6) forces the demand valve lever assembly (7) down. The pressure differential exists during the inhalation cycle of the user by creating a reduction in the pressure outlet (8). 4. Reduction in pressure at the pressure outlet is sensed in the demand diaphragm chamber (9) through the sensing port (10). 5 During periods of flow, the oxygen passes through the venturi assembly (11). At the venturi assembly, the flow of oxygen mixes with ambient air, which enters the regulator through the inlet ports (12). 6. The addition of ambient air to oxygen is controlled by the manual diluter control lever (13) and by the diluter aneroid assembly (14), which automatically produces a 100-percent oxygen concentration at altitudes above 32,000 feet. 7. The aneroid check valve assembly (15) prevents a flow of oxygen out through the inlet ports. 8. The emergency pressure control lever (16) applies force to the emergency pressure control test spring (17), which mechanically loads the emergency pressure diaphragm (25) through the control lever and center assembly (18). Mechanical loading of the emergency pressure diaphragm provides positive pressure at the regulator outlet. 9. Both automatic safety pressure and pressure breathing at altitudes above 30,000 feet are provided through pneumatic actuation of the aneroid assembly (19). This function begins near 27,000 feet altitude. The force exerted on the diaphragm assembly (20) by the aneroid assembly actuates the pressure breather valve assembly (21), and oxygen flows to the diaphragm and the plate assembly (22), which is pressure loaded by this volume of oxygen acting on the demand valve lever assembly to the extent that the positive pressure is built up at the pressure outlet as the altitude increases. 10. Additional safety is obtained through the inclusion of the second-stage relief valve assembly (23) in the regulator. TURNAROUND/PREFLIGHT/POST- FLIGHT/TRANSFER INSPECTIONS.— These inspections are visual inspections performed in conjunction with the inspection requirements for the aircraft in which the regulators are installed. Refer to table 4-3 for assistance in trouble- shooting. Visually inspect the following: 1. Electrical performance of the panel light 2. Legibility of all the markings 4-20 3. 4. 5. 6. 7. 8. 9. Plastic lighting plate for cracks and discoloration Low or improper reading on regulator pressure gauge Emergency pressure control lever in NORMAL position Diluter control lever in 100% OXYGEN position Supply valve control lever in OFF position Regulator and surrounding area free of dirt and hydrocarbons Delivery hose and connector for cuts, fraying, kinking, hydrocarbons, and general condition If discrepancies are found or suspected. maintenance control should be notified. Regulators that do not pass inspection and cannot be repaired in the aircraft are removed and replaced by ready-for-issue (RFI) regulators. Non- RFI regulators are forwarded to the nearest maintenance activity having repair capability. ACCEPTANCE/SPECIAL/DAILY IN- SPECTIONS.— These inspections are visual inspections followed by a functional test. These inspections and tests are performed in conjunc- tion with the inspection requirements for the air- craft in which the regulators are installed. Refer to table 4-3 for assistance in troubleshooting. WARNING Make certain that when working with oxygen, all clothing, tube fittings, and equipment are free of oil, grease, fuel, hydraulic fluid, or any combustible liquid. Fire and/or explosion may result when even slight traces of combustible material come in contact with oxygen under pressure. To perform the functional test, proceed as follows: 1. Place supply valve control lever in the ON position. 2. Place the diluter control lever in the NORMAL OXYGEN position. 3. Connect the oxygen hose to the quick disconnect, place the mask to the face, and inhale. Proper regulator operation will be indicated by the flow indicator assembly