Date: 201407
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: Mixed
Light: Dusk
Aircraft: B737 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
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Second reporter function: First Officer
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: Air Traffic Control Provided Assistance; Aircraft Equipment Problem Dissipated; Flight Crew Returned To Departure Airport; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Landed in Emergency Condition; Flight Crew Landed As Precaution
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Climbing through approximately FL180; I was notified by the X Flight Attendant (F/A) that there was a faint odor of smoke in the cabin. The X and Z flight attendants smelled what they thought might be smoke during takeoff and got up to investigate after passing 10;000 FT. They discussed the odor and decided to report it to the cockpit. I requested a description of the odor and a possible point of origin. The Y Flight Attendant came forward and said he smelled a faint odor of smoke. The X Flight Attendant said the odor was most noticeable near Row 8 and though the smell was dissipating although it was still there. There was no visible smoke and no passengers mentioned the smell or effects of smoke throughout the incident. There were storms around and much of the departure and the first half of the return were flown picking our way around the heavier parts of the storms. We were about eighty miles northeast of our departure airport and climbing through about FL260 when I decided to return to the airport. The First Officer requested the change of destination from ATC. We were turned ninety degrees and were assigned FL280. The flight attendants were tentative in their description of the smell and delayed their investigation so I initially considered returning to land as a precaution. I then decided that [advising ATC] and using the QRH would be the most prudent course of action. We were given vectors to the airport; and the First Officer and I completed the boxed items of the Smoke/Fire/Fumes on the Aircraft Checklist. I was focused on returning to the airport and getting on the oxygen mask and; had the First Officer not been holding the QRH in his hand; I may not have run the remainder of the checklist for a while. The flight attendants reported that the smoke smell continued to dissipate but was still identifiable. We were about one hundred miles northeast of the airport; and I briefly looked at the route map on the electronic flight bag to see if there was a closer suitable airport. I didn't recognize any airport identifiers near our location so I elected to continue to our origination airport. I did not ask ATC about the closest suitable field. My delay in [advising ATC] and not asking about a closer suitable airport may have been bad choices had there been an active; but unidentified fire. The First Officer was prepared with the QRH and we completed the checklist using the right column because the source of the odor could not be determined. The gasper fan had been inadvertently left on passing 10;000 FT and was turned off during the checklist execution. I told the flight attendants to notify the passengers of our return because I thought it might be difficult to communicate over the PA using the oxygen mask. The First Officer contacted Operations; requested a gate assignment; and asked that they contact Dispatch and inform them of our return. The Off Schedule Descent light illuminated while the First Officer was talking with Operations so I set our new temporary cruise altitude in the pressurization control panel. The approach and landing were uneventful. Multiple fire trucks and rescue vehicles were standing by and followed us to the gate; and Operations was prepared for our arrival. It was difficult to open the entry door because I reset the pressurization controller; defeating the return to airport function; so I released pressure using the cockpit escape window. We were met by an agent; two customer service supervisors; and two mechanics. The passengers deplaned and the aircraft was removed from service. We debriefed the incident and discussed our fitness for duty. We all agreed we were able to continue with our duty day; and a replacement aircraft was assigned and we departed a few hours later.If smoke is reported by the flight attendants; I should not hesitate getting the airplane on the ground. I need to do a better job scanning the pressurization panel passing 10;000 FT to verify the gasper fan is off. Using the divert guidance on the back of the normal checklists would have helped me organize my plan and would have mitigated my mistake of resetting the cruise altitude of the pressurization controller.


Second narrative: [Report narative contained no additional information].


Synopsis: On climbout through approximately FL180 the crew of a Boeing 737 was notified by a Flight Attendant of a faint odor of smoke in the cabin. When a definitive determination of the nature and seriousness of the event could not be made; the Captain returned to the departure airport.