Date: 201906
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: Marginal
Aircraft: A319
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ; Tower ZZZ
Aircraft component: APU Pneumatic System & Ducting
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Troubleshooting
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Attendant; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: After takeoff; First Officer asked me if I smelled that odor. I immediately recognized a dirty socks odor. We discussed it momentarily. We continued to climb as the First Officer called the flight attendants who reported the same odor throughout the cabin. I told ATC we needed to return to the field. During this time; I told the First Officer to don his O2 mask as I did the same. I then called for the QRC Fumes/Odor Checklist. We completed the checklist and prepared for landing back at ZZZ. I made a PA to the passengers to tell them we had an odor in the aircraft and were returning to ZZZ. The First Officer also contacted Dispatch and Local Ops on the radio. First Officer did a very professional job in assisting me the whole time. My O2 mask face shield was dirty and hard to see out of; so at apron 1;000 feet AGL; I removed my mask in order to land the aircraft. After we cleared the runway; I put my mask back on and wore it until after we shut down at the gate. We had paramedics meet us. The whole crew was transported to the hospital. The APU had an oil leak that got into the bleed air system. Please check the APU and engine seals for leaks!


Second narrative: On initial climbout; detected a strong odor that we believed were some type of fumes. I asked the Captain if he smelled something and he confirmed the odor I was smelling. We then donned oxygen masks. I then contacted the flight attendants via interphone and asked if they detected an odor. They all said they did. We then went through the Smoke and Odor checklist in our QRH and ended up turning off both packs. The decision was then made to return to ZZZ. We were given vectors back to the airport for ILS approach to ZZZ [Runway] XXR. Approach and landing were uneventful as well as taxi to gate where we exited the aircraft after jet way was brought to airplane. [I] believe there was some kind of oil or possibly hydraulic leak that was allowed to enter bleed air. Bleed air systems that do not get air from engine where it could be contaminated by oils or hydraulic fluid. [I suggest] better maintenance procedures to ensure seals are intact to prevent contaminated air.


Synopsis: A319 flight crew reported precautionary return to departure airport due to a 'dirty socks' odor throughout the aircraft.