Date: 201911
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Air Conditioning and Pressurization Pack
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)
Human factors: Situational Awareness
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Passenger; Person Flight Attendant
When detected: In-flight
Result: Aircraft Equipment Problem Dissipated; Flight Crew Overcame Equipment Problem
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Approximately 30 to 60 minutes after reaching cruise at 36;000ft; The A FA (Flight Attendant) contacted the flight deck to inform us that 3A PAX (passenger) reported a strange smell. The passenger described the smell as a transient burn odor. Passengers next to 3A reported not smelling anything abnormal. A FA also reported not being able to detect any abnormal odor anywhere in the cabin. I instructed the A FA to keep monitoring the situation and to report any change. About 30 to 45 minutes later; A FA reported that a passenger next to 3A now has also detected the strange odor and that 1A PAX is reporting not feeling well but did not smell anything abnormal. At that point I'm assuming 1A is probably unrelated to the odor at row 3. I instructed the FAs to turn the oven off and to keep monitoring. I also switch the pack flow control from low to norm to help clear lingering odor quicker. About 30 to 45 minutes after; we are getting reports that a couple more passengers at row 5 and 8; as well as the B FA and a non-rev FA have now noticed a strange odor. The A and C FA have not detected anything abnormal; but the A FA is reporting not being able to smell anything because she is experiencing burning sensation in her nose; eyes; and throat. The C FA reported the odor as resembling 'the smell when you open a gas oven'; 'sewage'; or 'dirty socks'. I asked if it smelled like sulfur and she replied 'yes!'. The odor is elusive; transient and of moderate intensity. The C FA is reporting having a light headache. We are now assuming the source might be AIR COND. I applied part of the SMOKE/FUMES/AVNCS SMOKE for AIR COND and turn Pack 1 OFF and ACARS Maintenance that we were experiencing a cabin air quality event. For the remainder of the flight no one detected any abnormal odor. PAX 1A reported feeling well approximately 30 minutes after turning pack 1 OFF. A FA filled a cabin air quality event form. I determined from the FOM Air Quality table that it was a severity level 2 event. Before the flight; Maintenance worked on engine #1 to replace an HPV (High Pressure Bleed) valve. During Post flight debrief with FA; everyone felt fine. Additionally; they reported thinking at one point that it 'smelled like a gas leak'. I made a logbook entry and contacted [Flight Ops Dispatcher] as per FOM. After sending an ACARS message to maintenance; we received no acknowledgment. I sent a message to dispatch half an hour later to asked if they had received my first message and they acknowledged they did. I think it would be nice to receive an acknowledgment.




Synopsis: A320 Captain reported Flight Attendant notification of passengers reporting abnormal odor at various times during flight. Flight Attendants also detected 'dirty socks/sulfur' odor during flight. Flight crew completed Air Conditioner fume QRH procedure which caused odor to dissipate.