Date: 202102
Local time of day: 0001-0600
Location: ZMP.ARTCC, MN
Flight conditions: VMC
Light: Daylight
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class E ZMP
ATC / advisory: UNICOM ZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Troubleshooting
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Clearance; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Attendant
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Aircraft Equipment Problem Dissipated; Flight Crew Landed in Emergency Condition; Flight Crew Overcame Equipment Problem; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Returned To Departure Airport; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: I was in command of Aircraft X schedule service from ZZZ to ZZZ1. We departed normally and were climbing to our assigned altitude of 32;000 ft. when just prior to level off our Flight Attendant called us in the cockpit to report that she had a smell of smoke in the cabin. We maintained communication with her as she said it seemed to be coming from Row 4 emanating from the lighting valance on the aircraft left side. We told her to monitor the situation and let us know if there was any sparking visible. She told us that she physically checked the valance and PSU's and they were very hot to the touch and that the smoke and heat was migrating rearward now from Rows 4 thru 10. I told the FA to get the PBE [Protective Breathing Equipment] out along with the fire extinguisher and prepare to fight a fire if one erupted. I then told the FO (First Officer) to notify ATC of our situation and that we needed to return to ZZZ. We were then cleared to return and given a decent clearance to 24;000 ft. Still not sure what type of smoke we had in the cabin I asked the FA to come forward so we could have the FO check the smoke for type of odor (electrical or engine based). FO advised me that the smoke odor seemed to have been not electrical. I then had him get the QRH out and run the procedure for SMOKE IN THE CABIN procedure. We accomplished the memory items and in coordination with ATC requested priority handling and were given an unrestricted decent to 8;000 ft. and vectors to a visual approach to Runway XX at ZZZ. The ARFF (Airport Rescue and Firefighting) trucks were standing by for our arrival. The QRH procedure was completed and the smoke seemed to dissipate a little according to the FA. We landed without incident and upon initiation of communication with the ARFF commander we were told there was no smoke evidence on the exterior of the aircraft. Since it appeared the internal situation was under control we decided to taxi to the gate for normal deplaning. Fire Dept. followed us to the gate and upon arrival ; they boarded the aircraft and I advised the commander of what had happened and where it had been located. The ARFF members then checked the aircraft over with their thermal heat locater and found no heat source in the Valance or PSU. They then left the aircraft. Dispatch and MX were notified of the situation. Aircraft passengers were deplaned without incident.




Synopsis: Captain reported an uneventful diversion due to reported fumes of smoke in passenger cabin.