Date: 201605
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Aircraft: A319
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Aircraft component: Oxygen System/Crew
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Other / Unknown
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: General Flight Cancelled / Delayed; General Maintenance Action; General Release Refused / Aircraft Not Accepted
Contributing factors: Aircraft; Procedure
Primary problem: Ambiguous

Narrative: While reviewing the maintenance status I noticed that on two occasions in the last eight days the crew oxygen had been serviced due to low pressure; 900 PSI and 980 PSI respectively. During preflight the First Officer and I discussed the oxygen pressure; it was reading 1;100 PSI at the time; and we agreed to keep an eye on it during the flight. Approximately midway during the flight the oxygen pressure dropped to 970 PSI so I sent a maintenance code for servicing and noted the pressure in the remarks.On arrival I went to the flight planning area to flight plan [for the next leg]. Before leaving the flight deck I told the First Officer to tell the maintenance technicians that even though the oxygen pressure was above minimums I needed it to be serviced before departure unless they didn't have oxygen in stock.Despite the First Officer's best efforts to convey my intent to the maintenance technicians working our flight; they deferred it. When I returned to the flight deck and learned it had not been serviced I contacted Maintenance Control. Maintenance Control was supportive to my request and suggested if I would refuse the airplane the oxygen would likely be serviced. I had already thought of that; and that was why I called them.After refusing the airplane; someone in local maintenance; called the gate and required us to deplane all the passengers before they would service the oxygen and said they would need approximately one hour to accomplish the procedure. I know from experience both those requirements are false; but by the time I called Maintenance Control to confirm the bit about deplaning passengers; the deplaning was nearly complete.I called station hub maintenance to make sure I was doing everything I could do to expedite the process. Hub maintenance sent a lead mechanic to the plane. I explained to the lead that this airplane has a recent history of oxygen needing to be serviced. During my flight the pressure had dropped more than 100 PSI (some likely due to temperature factors); which I feel was significant. Additionally some months earlier I had an oxygen hose burst loose from my mask at 35;000 feet; so I am especially cautious about low oxygen. I let him know even though it was above the minimum required; it was important to me to have it serviced and that it was a safety of flight concern for me.The lead mechanic told me they would have to find some bottles to service the oxygen; but when they connect the bottles the pressure equalizes and it is never enough and it would take considerable time. After the mechanic left I called dispatch so he was aware of our delay. The passengers started reboarding after being off the airplane for about 15 minutes; but before the oxygen service began.The maintenance release finally printed and we pushed back 1 hour 31 minutes after block in. This was a disappointing and frustrating experience for everyone involved; especially our passengers.Additionally; the ground crew called me approximately ten minutes earlier and told me to release the brakes. At that time the jet bridge was still attached and door 1L and the aft cargo door were both open. I thought something was wrong so I asked him why he wanted the brakes released and he said they were ready. I told him about the loading bridge and the two doors and we were waiting for a maintenance release.




Synopsis: A319 Captain reported flying an aircraft with a history of crew oxygen replenishments. On this leg the pressure dropped over 100 pounds and the Captain requested replenishment upon arrival even though the pressure is not below minimums. This request is met with a great deal of resistance by local Maintenance causing a departure delay.