Date: 202012
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Aircraft: A321
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Aircraft component: Coalescer Bag
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Second reporter function: Pilot Flying; First Officer
Anomaly: Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Crew
When detected: Routine Inspection; Pre-flight
Result: Flight Crew Overcame Equipment Problem; General Maintenance Action; General Flight Cancelled / Delayed
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: During passenger boarding I started the APU to cool the aircraft. I selected the APU bleed on and immediately began to smell a foul pungent odor. I turned the bleed off and waited a couple minutes. I tried the APU bleed again and encountered the same pungent odor. I waited a minute to see if it was a temporary smell but it persisted. I turned the bleed off and wrote up the airplane in the maintenance logbook. The smell was predominantly in the flight deck and forward galley however passengers deplaning from the rear of the aircraft were inquiring about the odor. Maintenance checked to see if the APU was possibly over serviced. The APU checked out normal. Maintenance continued their work and eventually cleared the write up. When we returned to the aircraft to get ready to board all crew members again smelled the same smell. Although it was not as strong as before it was still there and seemed to get slightly worse if we turned the Number 1 Pack off. I again wrote the aircraft up in the maintenance logbook. No medical attention was requested or required for crew or passengers.As for the probable cause; no causal factors that I can think of. Maintenance said it could have been the fumes from an aircraft starting upwind of us however that wouldn't explain why we smelled it the second time hours later.


Second narrative: APU was started in preparation for departure; upon turning on the APU bleed to begin cooling the aircraft there immediately was a strong fume that made my nose and eyes begin to burn. I told the CA (Captain) that was the bad fume smell we need to be careful about and said I was leaving the flight deck to stand on the jet bridge. The bleed was turned off and I left for fresh air. After multiple retries by MX (Maintenance) who agreed the smell was there the passengers and remaining crew were deplaned. Later the MX personnel had done nothing other than run the packs using the external air cart and were ready to sign the plane back into service; but simply walking into the galley every single crew member could still smell the fumes. We tried to isolate the problem pack by switching packs and the fumes became worse again. We then left the aircraft again. This is an ongoing problem worldwide in the industry. The potentially disastrous health consequences of this type of pyrolization should be addressed before more crew members and passengers are impacted.


Synopsis: A321 flight crew reported a fumes event during passenger boarding resulting in maintenance action.