A320
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 92.82; Flight Crew Total 1087.45; Flight Crew Type 1087.45
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Other / Unknown
Flight Crew Overcame Equipment Problem; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Landed in Emergency Condition
Aircraft
Proceeding directly to ZZZZZ intersection on the ZZZZZ 2 RNAV arrival. Was cleared to descend via ZZZZZ 2 RNAV arrival on [Runway] XXR. Prior to ZZZZZ; at approximately FL220 during descent; noticed that the cabin altitude was at 8;300 feet and increasing. I called attention to the First Officer that we might be losing cabin pressurization. The Pressurization screen on ECAM was displayed and noticed that both the inlet and extract valve were fully closed but the safety valve had opened.Since we had already been cleared to descend via ZZZZZ arrival and had an altitude of 12;000 set in the MCP I decided to expedite the descent to see if I could control the rate of ascent in the cabin. At approximately FL180 it appeared that we could not control the rate of ascent in the cabin and that at its present rate the cabin would exceed 10;000 feet shortly. I then [advised] with ATC and requested 10;000 feet which was granted. I advised the Lead Flight Attendant that we were experiencing cabin pressurization problems but to expect a normal landing. As we leveled at 10;000 feet I monitored the cabin and noticed that it had climbed to 12;000 feet but stabilized. It took several minutes before the cabin normalized at our cruise altitude of 10;000 feet. I asked the First Officer  to see if he could find an applicable checklist to run. During this time I maintained control of the aircraft and communicated with ATC. The First Officer advised that he was able to manually control the outflow valve and that the checklist recommended shallow descents thereafter. I continued to ask for delayed vectors from ATC just north of ZZZ as the First Officer and I reviewed the state of the aircraft and decided it was safe to proceed with the landing. I asked ATC for shallow descents on the arrival to [Runway] XXR into ZZZ. The landing and taxi in were uneventful.
Air carrier Captain reported malfunctioning pressurization system on descent.