Date: 201503
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: IMC
Aircraft: Dash 8 Series Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Attendant
When detected: In-flight
Result: Flight Crew Diverted; Flight Crew Landed As Precaution
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: Approaching FL180 we received an emergency call from the 'A' flight attendant notifying us that there was a little haze and the smell of 'a burning belt on a vacuum'. I told her we that we would get right back to her. I transferred the controls to my first officer. I told ATC to standby and then pulled out the QRH and started to run the fuselage smoke checklist. My first officer and I at no point during the emergency could smell smoke or any other anomalies. We also never saw any haze nor smoke either. I referenced the fuselage smoke or fire page. In the checklist it states under Unknown Source of Smoke or Fire you can choose Bleed Source or Air Conditioning Suspected. I called the flight attendants and asked where the haze and smell was. I was told that it was located between rows 15 and 20 and it was only in that area. I felt that the central location was a possible electrical issue so I continued to the Source of Smoke or Fire Cannot be Identified section of the checklist. I began that portion of the checklist which directs you to turn off the DC and then the AC generators. As I started turning off the generators I decided to turn them back on because we were at night and would have to return through IMC and possible icing on our return.  I felt that I would try the more conservative approach of the checklist and run the Bleed Source or Air Conditioning Suspected. Once I turned the bleed air 1 off I called the flight attendant and she said the smell and haze had improved. At that point I told the 'A' flight attendant that we are not sure of the source of the smell but that she had approximately 20 minutes to land; no specials; and no brace command. I contacted ATC and told them that we would be returning and that we wanted emergency equipment. We also asked for a descent and continued directly. I sent an ACARS to dispatch informing them that we were diverting for a burning smell. I then made a PA informing the passengers that we were returning. I then took the controls back from the first officer. We were vectored to the ILS and landed without incident. I turned off the runway and contacted the emergency equipment to circle our aircraft for any abnormalities. The emergency equipment said they noticed nothing abnormal and followed us to the gate. We deplaned the passengers and met with maintenance. I did not smell or observe anything abnormal once we were parked at the gate.A few days later I had a conversation with our program manager about the emergency event.  We went step by step through the emergency and discussed which actions I had taken and why I decided to go that route.  I feel that after the discussion I should have asked more questions to our flight attendants to try and narrow down what may have been the cause of the event and taken more time to decide the correct course of action.  I should have ran the QRH Bleed Source or Air Conditioning Suspected which would direct me to turn off the bleed air. The turning off of the bleed would have improved our situation.  I should have also immediately had the first officer contact ATC and have ATC take us back immediately. I also feel that I should have not have started turning off AC and DC generators per the QRH when that could have put us into an electrical emergency. The situation may have been as simple as a bird being ingested causing the smell. The correct course of action would have been to take a deep breath; question the flight attendants in more depth; and start with the more conservative action of turning the bleed source off.




Synopsis: A DHC8 Captain is informed of smoke in the cabin by the lead Flight Attendant; and choses to follow the Source of Smoke or Fire Cannot be Identified QRH. This procedure turns off DC then AC generators; which seems a poor idea at night and returns to the bleed source or air conditioning suspected and turns off bleed air 1 with positive results. Flight returns to the departure airport.