Date: 202105
Local time of day: 1801-2400
Location: ZZZ.ARTCC, US
Aircraft: A321
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: 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 Not Flying; First Officer
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance; Flight Deck / Cabin / Aircraft Event Illness / Injury; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor; Inflight Event / Encounter Other / Unknown
Detector: Person Flight Crew; Person Flight Attendant
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Diverted; Flight Crew Landed in Emergency Condition; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Overcame Equipment Problem; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: FA (Flight Attendant) called as we were climbing to FL280 reporting dirty sock odor from Row 26 aft to galley. No odor in rest of cabin. No odor detected in flight deck. Asked FA to check lav; overhead bins; galley carts and storage areas. Nothing was found. Began getting data for landing in ZZZ1. Began referencing QRH for smoke procedure and overweight landing procedure. FO (First Officer) assumed Pilot Flying duties and ATC. FA (flight attendant) then informed us that occupants were becoming ill. We immediately notified ATC and requested diversion to ZZZ1. Informed ATC we had injuries. Sent ACARS to Dispatch advising of diversion. During descent completed QRH Overweight Landing procedure and began Smoke/Avionics Smoke/Fumes QRH 17-1 procedure. Stopped Smoke procedure while maneuvering for approach and assumed Pilot Flying duties. Uneventful overweight landing. Stopped aircraft on runway and called FA's to assess. Was notified that the odor had stopped. Requested taxi to gate. Taxied per ATC instructions to ramp. Ramp unaware of our condition and asked us to hold on the ramp. Attempted contact with Operations. No answer. Ramp was able to obtain gate information from company and cleared us to gate. Fire truck followed us to gate and fireman came onboard and said all was clear outside of aircraft. Requested paramedics. Waited for over 15 minutes to arrive. FA 3 and several passengers were ill and required treatment. Informed that odor had completely subsided. Passengers remained onboard to allow access for paramedics as ill occupants were blocking front galley area and jetbridge. Flight Attendants were very assertive in communicating the specifics of the odors and location including the condition of our passengers throughout the event. This played a significant role in understanding the condition in the cabin and making proper decisions. Odor events can be difficult to prevent. Preparing for these seemingly inevitable challenges can make them easier to manage.


Second narrative: Climbing through FL240 on our way to our final FL280 we receive a call from the (FAs) flight attendants. The Captain took the call because I was responding to a frequency change to ATC. After checking in with Center I noticed the call with the FAs was taking longer than most so I decide to listen in. I overheard that the one of the flight attendants was reporting a weird smell in the back of the aircraft. After hearing a very brief snippet I pulled out my QRH and located fumes on page 17-2 just as a precautionary measure. The Captain returns from the call and informed me of what was taking place and that he was trying to receive more information from the FA's. During this time we had leveled at our cruise altitude of FL280; and our closest airport was ZZZ1. We decide to see what the weather was in ZZZ1. The weather was VFR conditions landing west. The FA calls back; I tell the Captain my aircraft; my radios so he can direct all this attention to the issue at hand. As he was talking to the FA's I overheard that they trying to figure out what the odor smells like. I look down and at the bottom of 17-2 is an odor/toxic substance checklist on 15-32. I flip to that page and hand the QRH to him. The Captain returned from the call and informed me that it smelt like a dirty sock/wet dog and that we have injuries on board; we are diverting to ZZZ1.  After that the Captain hands me back my QRH and starts the smoke/avionics smoke/ fumes QRC /QRH procedure. As we start descending I notice our aircraft gross weight was at 180;200 lbs and that we are going to be landing overweight so I turned my QRH to 15-22 over weight landing. After finishing the fumes QRC I hand the Captain my QRH so he can start that procedure. Shortly thereafter ATC asked what runway we would like and after making the landing calculation the Captain determined XXR would be the safest runway to land on. I put the ILS XXR in the box and sequenced it accordingly. After the Captain finished the overweight landing QRC; he resumed Pilot Flying duties; I resumed Pilot Monitoring duties and he asked for descent checklist as we were on a base leg for XXR. We were cleared the approach; we fully configured the aircraft; ran the before landing checklist. On short final I asked Tower to have safety vehicles standing by and that we were going to stop on the runway. The Captain landed the aircraft smoothly around 179;000 lbs; 148 knots and vertical speed around 100 ft a minute. We stopped on the runway; the Captain informed the passengers to remain seated three times. ARFF told us the aircraft looked fine and we taxied to the gate. Reporter suggested Airbus needs to determine what causes these mysterious 'dirty sock' fume events and provide a fix.


Synopsis: A321 flight crew reported a dirty sock" odor was detected in the cabin during cruise resulting in a diversion."