Date: 202109
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: VMC
Aircraft: A319
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
ATC / advisory: TRACON ZZZ
Aircraft component: Cooling Fan; any cooling fan
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Second reporter function: Pilot Flying; First Officer
Anomaly: Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Aircraft Equipment Problem Dissipated; Flight Crew Overcame Equipment Problem; Flight Crew Requested ATC Assistance / Clarification; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: About 20 miles from TOD (Top of Descent); the FO (First Officer) and I noticed a slight acrid smell. I directed us to don our oxygen masks. It seemed that as soon as we did that; we heard and felt a light rumbling sound from below the flight deck. It sounded like a fan starting to fail. We ran the entire smoke and fumes checklist at that point; and after turning off the fans; the sound stopped. The Lead Flight Attendant had also called up and said that there was a slight smell at first; but didn't notice it anymore. I explained to him what was going on; and that I'd call him back once we decided how we wanted to proceed. The FO and I agreed that being so close to descent; with the arrival and approach having already been briefed; with the fumes situation stabilized; it was best to continue into ZZZ. I [advised ATC] at that point; asked for clearance to fly the STAR and approach for [Runway] XXR; and to have crash and fire rescue available. ATC cleared us as requested. I then sent a 'call me' to dispatch. I explained to him what was going on; that the situation was stabilized; and that we were planning on continuing to ZZZ. He did not have anything for us and said that was a good idea. I then phoned the Lead FA; and gave him the [plan] information; and let me know if they needed anything. Since it was late at night; it was the last leg of a 3 leg day; were already on the descent and needed to pay attention to the terrain in the area; and we had already had a rejected takeoff on the same flight; I elected to not mention anything to the passengers. Having me come in the PA with an oxygen mask; telling them that there are fumes in the airplane (again; the problem seemed to have been isolated and situation stabilized); after they just experienced a rejected takeoff; was only going to cause them more undue stress. Instead; I told the Lead FA to tell them something in general terms that there was an issue; but it's now stabilized. The arrival and approach were uneventful; and we elected to taxi to the gate. I told the FO to make an announcement to the passengers to remain seated while we have the fire department come on board to check something out on the Flight Deck. He did. After we pulled into the gate; we shut down the engines; but left the seat belt sign on. The fire department was already walking up the jet way stairs almost as soon as we shut down the engines. After the main door were open; two guys came onboard with some sensor equipment. We took off our oxygen masks at that point since they didn't have theirs on. They said their sensors were showing the air was safe. As soon as they were done and off the plane; we turned off the seat belt sign. After we were deplaned; I called the [Chief Pilot]; gave him a rundown of what happened. Then I called Dispatch and did the same thing; and had him patch me through with Maintenance. I talked to them for about 10 minutes; and filled out their smoke and fumes report. ZZZ Maintenance was on board by this time and were already looking at the plane. They told us to terminate it; leaving the switches that we turned off for the smoke and fumes checklist. We terminated it and left for the hotel.


Second narrative: I was Pilot Flying. Just prior to Top of Descent I smelled a sudden order of what smelled like sulfur/fireworks followed by a intermittent humming noise on my right side. We both put on our masks and we ran the smoke/fumes checklist. While we were completing the checklist; the Flight Attendants also called up saying they smelled something as well. The Captain told them to keep us informed if it was getting worse and we continued with the checklist. After putting the blower and extract fans in override per the checklist the noise on my right side stopped. At the same time we coordinated with Air Traffic Control to start down on the arrival and also the Captain [requested priority handling]. The smell did not get any worse but as a precaution we kept our masks on for the rest of the flight. We landed safely and taxied to the gate where we were met by firemen who sampled the air and found no hot areas and we deplaned the passengers normally.


Synopsis: A319 flight crew reported a fume event during cruise. The flight continued to destination and after an air quality check at the gate; passengers and crew deplaned safely.