Narrative:

The entire crew was aware and briefed by the captain that this aircraft was late into ZZZ due to a previous fume event the day prior and wanted to make sure everyone was aware of the proper procedures on how to handle a fume event. Prior to boarding the C flight attendant (F/a) made the cockpit crew and all other F/a's aware that she smelled only what she could describe as a 'smelly foot' smell in the aft galley. The entire crew went back to the aft galley to investigate if they smelled the same odor. Not one single crew member could verify what the c-f/a smelled so with 4 out of 5 crew members all in agreement that is was nothing to worry about; we proceeded to board the passengers. After a lengthy delay from the aircraft being late to ZZZ and a MEL addition; we finally departed the gate. Everything was normal up until after takeoff and above 10;000ft MSL we got a call from a F/a saying that there was a dirty sock smell now coming from the forward galley and went all the way to approximately row 10. By this time we were somewhere around FL250 climbing to FL380. The captain spoke to the F/a's while I handled the flying. The captain told me that all 3 F/a's now could confirm the same smell and it was the 'dirty sock' smell. The captain and I donned our O2 masks immediately then the captain asked me to tell ATC we needed to level off; slow down and enter a present position hold so we could deal with an issue. ATC complied and we leveled off at FL300 and slowed to 250kts and entered into a present position hold right hand turns with 10 mile legs. The captain took the controls of the airplane while I ran the fume/odor event checklist from zzzzz. It took about 10 min to run the check list due to the 3-5 min waiting period per pack to see if the fume/odor disappeared. The F/a's told us after each pack and been selected to off and after the waiting period that the smell had not gone away. Per the checklist; if the odor had not disappeared; you are to land as soon as possible. At that time the captain gave the controls of the plane back to me and he then proceeded to declare with ATC and asked for immediate vectors back to ZZZ. The captain notified the F/a's that we were headed back to the airport and that they should prepare the cabin for arrival and if they needed for safety to use the O2 for themselves. Since we had notified ATC and as the pilot flying I kept the speed up as much as possible so we could get people and ourselves out of a dangerous situation as quickly as possible I flew above 250kts below 10;000ft MSL. And then when ATC gave us a heading to vectors for the ILS runway xx into ZZZ due to the tense situation and difficulties hearing and speaking with the O2 masks on which made crew coordination very difficult; we turned to the wrong heading but was quickly corrected when ATC asked us to confirm our heading. We had turned to a 030 heading when it should have been a 100 heading. With the heading issue corrected; we made it to the ground without incident. After exiting the runway tower control asked us to utilize a high speed taxiway for exiting the runway and come to a stop clear of the runway hold short markings so that airport ops crews could inspect the plane. The passengers were then de-planed by a bus that is utilized in ZZZ there on the taxiway and after the fireman were onboard the plane with some sort of device that can determine air toxicity; they told myself and the captain that it was unsafe levels of CO2 in the cabin so the captain and I shut the airplane completely down; even waiting the 2 min waiting period for the APU to shut down before turning the batteries off and ensuring the plane was chocked; releasing the parking brake so that the plane could be towed; the captain and I were the last people off the airplane with only fire crews left on the plane.

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Original NASA ASRS Text

Title: Airbus A319 flight crew reported a dirty sock smell from the forward galley resulted in a return to the departure airport.

Narrative: The entire crew was aware and briefed by the captain that this aircraft was late into ZZZ due to a previous fume event the day prior and wanted to make sure everyone was aware of the proper procedures on how to handle a fume event. Prior to boarding the C Flight Attendant (F/A) made the cockpit crew and all other F/A's aware that she smelled only what she could describe as a 'smelly foot' smell in the aft galley. The entire crew went back to the aft galley to investigate if they smelled the same odor. Not one single crew member could verify what the C-F/A smelled so with 4 out of 5 crew members all in agreement that is was nothing to worry about; we proceeded to board the passengers. After a lengthy delay from the aircraft being late to ZZZ and a MEL addition; we finally departed the gate. Everything was normal up until after takeoff and above 10;000ft MSL we got a call from a F/A saying that there was a dirty sock smell now coming from the forward galley and went all the way to approximately row 10. By this time we were somewhere around FL250 climbing to FL380. The captain spoke to the F/A's while I handled the flying. The captain told me that all 3 F/A's now could confirm the same smell and it was the 'dirty sock' smell. The captain and I donned our O2 masks immediately then the captain asked me to tell ATC we needed to level off; slow down and enter a present position hold so we could deal with an issue. ATC complied and we leveled off at FL300 and slowed to 250kts and entered into a present position hold right hand turns with 10 mile legs. The captain took the controls of the airplane while I ran the fume/odor event checklist from ZZZZZ. It took about 10 min to run the check list due to the 3-5 min waiting period per pack to see if the fume/odor disappeared. The F/A's told us after each pack and been selected to off and after the waiting period that the smell had not gone away. Per the checklist; if the odor had not disappeared; you are to land ASAP. At that time the captain gave the controls of the plane back to me and he then proceeded to declare with ATC and asked for immediate vectors back to ZZZ. The Captain notified the F/A's that we were headed back to the airport and that they should prepare the cabin for arrival and if they needed for safety to use the O2 for themselves. Since we had notified ATC and as the pilot flying I kept the speed up as much as possible so we could get people and ourselves out of a dangerous situation as quickly as possible I flew above 250kts below 10;000ft MSL. And then when ATC gave us a heading to vectors for the ILS RWY XX into ZZZ due to the tense situation and difficulties hearing and speaking with the O2 masks on which made crew coordination VERY difficult; we turned to the wrong heading but was quickly corrected when ATC asked us to confirm our heading. We had turned to a 030 heading when it should have been a 100 heading. With the heading issue corrected; we made it to the ground without incident. After exiting the runway Tower control asked us to utilize a high speed taxiway for exiting the runway and come to a stop clear of the runway hold short markings so that airport ops crews could inspect the plane. The passengers were then de-planed by a bus that is utilized in ZZZ there on the taxiway and after the fireman were onboard the plane with some sort of device that can determine air toxicity; they told myself and the captain that it was unsafe levels of CO2 in the cabin so the captain and I shut the airplane completely down; even waiting the 2 min waiting period for the APU to shut down before turning the batteries off and ensuring the plane was chocked; releasing the parking brake so that the plane could be towed; the captain and I were the last people off the airplane with only fire crews left on the plane.

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.