First officer reported loss of cabin pressure after maintenance had replaced a cargo door sill; resu...

Narrative:

Require a pressure when replacing door sealsour original flight was delayed by 3 hours due to a mx write up from the flight crew that brought the aircraft in. They noticed a loud noise coming from the rear of the plane while inflight. Mx personnel found the rear cargo door seal needed to be replaced and did so. Once that was completed we boarded up the plane and took off for ZZZ. While climbing out through approximately FL280; the captain and I notice the pressurization page pop up and the cabin alt flashing. The cabin altitude was climbing through 9000 at about 800-1000fpm. The captain and I decided to don our oxygen masks and shortly after the ECAM message for high cabin altitude came on. At this point the captain initiated an expedited decent and requested priority handling with center and I ran the ECAM actions. The captain descended and made a left hand turn back toward ZZZ1 away from the mountains. The flight attendants were notified by the captain. Once the cabin altitude was back below 10;000 and the ECAM had extinguished we removed our masks and continued with ATC instructions with vectors to ILS 25L into ZZZ1. We ran all normal checklist and briefed the arrival/approach. Dispatch was notified via ACARS and operations via coms. The approach and landing was uneventful. The aircraft was under max weight and no damage had occurred. It was a normal landing with a couple emergency vehicles standing by. The oxygen masks in the cabin did not deploy and there were no injuries to any person. One flight attendant reported a headache and another used one of the aircraft's portable oxygen units. Neither of them wanted any medical assistance. While at the gate; mx personal looked at the cargo door. It was their belief that the new door seal was faulty.

Original NASA ASRS Text

Title: First Officer reported loss of cabin pressure after maintenance had replaced a cargo door sill; resulting in an expedited descent and an air turnback.

Narrative: Require a pressure when replacing door sealsOur original flight was delayed by 3 hours due to a MX write up from the flight crew that brought the aircraft in. They noticed a loud noise coming from the rear of the plane while inflight. MX personnel found the rear cargo door seal needed to be replaced and did so. Once that was completed we boarded up the plane and took off for ZZZ. While climbing out through approximately FL280; the Captain and I notice the pressurization page pop up and the cabin alt flashing. The cabin altitude was climbing through 9000 at about 800-1000fpm. The Captain and I decided to don our oxygen masks and shortly after the ECAM message for high cabin ALT came on. At this point the Captain initiated an expedited decent and requested priority handling with Center and I ran the ECAM actions. The Captain descended and made a left hand turn back toward ZZZ1 away from the mountains. The flight attendants were notified by the Captain. Once the cabin altitude was back below 10;000 and the ECAM had extinguished we removed our masks and continued with ATC instructions with vectors to ILS 25L into ZZZ1. We ran all normal checklist and briefed the arrival/approach. Dispatch was notified via ACARS and operations via coms. The approach and landing was uneventful. The aircraft was under max weight and no damage had occurred. It was a normal landing with a couple emergency vehicles standing by. The oxygen masks in the cabin did not deploy and there were no injuries to any person. One flight attendant reported a headache and another used one of the aircraft's portable oxygen units. Neither of them wanted any medical assistance. While at the gate; MX personal looked at the cargo door. It was their belief that the new door seal was faulty.

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.

Attributes
ACN	1753458
Time
Date	202007
Local Time Of Day	1201-1800
Place
Locale Reference	SCT.TRACON
State Reference	CA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	A321
Operating Under FAR Part	Part 121
Flight Phase	Climb
Route In Use	Vectors
Flight Plan	IFR
Component
Aircraft Component	Cargo Door
Person 1
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural Published Material / Policy Deviation - Procedural Maintenance

First officer reported loss of cabin pressure after maintenance had replaced a cargo door sill; resulting in an expedited descent and an air turnback.