Narrative:

Received an ECAM cabin altitude warning as we leveled at cruise altitude (FL350). I directed the donning of oxygen masks. Cabin altimeter showed cabin was climbing through 10;000 feet. After crew and jumpseater had checked in on intercom; we began an immediate descent and turned back toward [departure airport; after I] (coordinated with center). I directed the first officer (first officer) to descend at 320 knots until we leveled off (initially cleared to 7;000 feet; then 5;000 feet). We made an initial reaction to manually close the outflow valves to stop the cabin from climbing. Outflow valves were already indicating full closed. Cabin continued to climb to at least 12;000 feet. Completed ECAM items and referred to QRH for cabin attendant press man control; which basically directed the same actions. Passing through 10;000 feet; cabin and aircraft altitude matched; and we removed our masks. First officer had a tough time with mask; as one of the connection points was disconnected. I directed the first officer to continue above 250 KTS below 10;000 feet. I assessed that the pressurization system was not responding to manual outflow control--appeared to be unpressurized between 10;000 feet and 5;000 feet in the descent; matching cabin altitude; outflow valves full closed. I discontinued cabin attendant press man control procedure for this reason. We completed an uneventful landing. We taxied to parking. During taxi in; we noticed that the aircraft was pressurized. We used manual control to relieve the pressure before opening the door. I am not sure at what point the aircraft pressurized--at some point between 5;000 feet and taxi in. In hindsight; I could have avoided this by completing the cabin attendant press man control procedure; as it directs opening of the outflow valves before landing after cabin pressure and aircraft altitude were equal. This was a mistake on my part. At the time; I felt that the aircraft was not pressurized and could not pressurize. I chose to focus on a safe landing instead of continuing with the final steps of the procedure. First officer did a great job! Entries made in [maintenance log] for cabin altitude and first officer oxygen mask.

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Original NASA ASRS Text

Title: A300 flight crew reported returning to departure airport due to pressurization problems; later traced to a vent extraction fan ducting.

Narrative: Received an ECAM cabin altitude warning as we leveled at cruise altitude (FL350). I directed the donning of oxygen masks. Cabin altimeter showed cabin was climbing through 10;000 feet. After crew and jumpseater had checked in on intercom; we began an immediate descent and turned back toward [departure airport; after I] (coordinated with Center). I directed the FO (First Officer) to descend at 320 knots until we leveled off (initially cleared to 7;000 feet; then 5;000 feet). We made an initial reaction to manually close the outflow valves to stop the cabin from climbing. Outflow valves were already indicating full closed. Cabin continued to climb to at least 12;000 feet. Completed ECAM items and referred to QRH for CAB PRESS MAN CTL; which basically directed the same actions. Passing through 10;000 feet; cabin and aircraft altitude matched; and we removed our masks. FO had a tough time with mask; as one of the connection points was disconnected. I directed the FO to continue above 250 KTS below 10;000 feet. I assessed that the pressurization system was not responding to manual outflow control--appeared to be unpressurized between 10;000 feet and 5;000 feet in the descent; matching cabin altitude; outflow valves full closed. I discontinued CAB PRESS MAN CTL procedure for this reason. We completed an uneventful landing. We taxied to parking. During taxi in; we noticed that the aircraft was pressurized. We used manual control to relieve the pressure before opening the door. I am not sure at what point the aircraft pressurized--at some point between 5;000 feet and taxi in. In hindsight; I could have avoided this by completing the CAB PRESS MAN CTL procedure; as it directs opening of the outflow valves before landing after cabin pressure and aircraft altitude were equal. This was a mistake on my part. At the time; I felt that the aircraft was not pressurized and could not pressurize. I chose to focus on a safe landing instead of continuing with the final steps of the procedure. FO did a great job! Entries made in [maintenance log] for cabin altitude and FO oxygen mask.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.