Date: 202002
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: IMC
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
ATC / advisory: Center ZZZ
Aircraft component: Pneumatic System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Physiological - Other
Second reporter function: First Officer; Pilot Flying
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 Requested ATC Assistance / Clarification; Flight Crew Landed in Emergency Condition; Flight Crew Overcame Equipment Problem; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: The aircraft arrived the night before and overnighted in ZZZ1. We were to depart at XB:16 the next morning. The ambient temp at XA:15 when we arrived at the jet was -10 with a wind chill of -30.  During engine start the oil clog ECAM messages displayed momentary for both engines due to the extreme cold. Both FO (First Officer) and myself discussed the warm up of the engines. FO was the pilot flying the leg and the flight was non-eventful during cruise. There was a front approaching ZZZ and Dispatch was keeping us informed of the weather. I spoke to Dispatch inflight and we agreed to add ZZZ2 as an alternate due to the line of weather that was to the east of the field.  When we checked in with ATC we were told to expect holding on the [name] arrival at ZZZZZ at FL200. FO entered the hold and at this point the weather was between us and the field below our altitude. Since the descent would be around weather I called the flight attendants and had them prepare the cabin for landing and to remain seated for the remainder of the flight. After one turn in holding; at FL200; ATC told us we were going to be vectored to an arrival to the east of the field due to weather. As we started our descent; on a vectored heading; I started to smell a 'musty sock' odor.  I looked at FO and asked if he was smelling the same thing. He said yes and we both put on our O2 masks. I made a quick call to the back to check on the flight attendants. The number one said he didn't smell anything and the FAs (flight attendants) in the back said that she did smell 'some sort of odor'. I remember thinking to myself that I was starting to feel the same hypoxic symptoms I felt during Air Force altitude training. FO and myself assessed each other and we were both feeling much better with O2. At this point we were in a descent; on vectors; going to the east of the field for weather. I decided to notify ATC due to the fumes and not knowing if the cockpit would remain clear of haze because the onset of the fumes was so rapid. ATC quickly gave us vectors to runway XX in ZZZ. We stayed on O2 for the reminder of the flight. After landing and clearing the runway; I turned the aircraft bleeds and packs off. EMT and fire department personal checked passengers as they exited the aircraft. Cause: As I stated above the engines were cold soaked on startup. This odor has been linked to oil and oil seals in the engine and packs. Maybe the first real thrust reduction exposed a gap in one of the oil seals. Suggestions: This type of odor is associated with tricresylphosphate (TCP). When we landed Maintenance told us that the only way to test the aircraft was to start the engine on the ground and then smell for the TCP 'musty sock' odor. I find it unbelievable in a fume event like this that there isn't a procedure to take a swab of the cockpit or cabin to detect the presence of TCP; compound that would easily be found. There has to be residue left behind in the cockpit. When I went home I shower and scrubbed myself clean.


Second narrative: On descent into ZZZ in IMC; Captain and I detected an unusual odor. We donned our masks. I was pilot flying so I maintained control of the aircraft while the Captain spoke with the FAs (flight attendants) and ran the QRH. [We notified ATC] and we proceeded direct to ZZZ while deviating around some strong radar returns. Landed without event and taxied with priority to the gate. Aircraft was removed from service. My only suggestion would be immediate removal from duty. The Chief Pilot laid out our options; but left it up to us to decide if we were fit to continue duty. It took some time to self evaluate after the adrenaline wore off; and I'm glad we went to get evaluated by a medical professional.


Synopsis: A320 flight crew reported a fume event during initial approach resulted in the crew donning oxygen masks and continuing to destination.