Narrative:

During cruise; flight attendants (flight attendant) notified me of an acrid and electrical smell in the forward cabin. No fumes observed in cockpit. Coincidently the right recirculation fan momentarily failed and returned to functioning status with no crew interaction. QRH for recirculation fan is a crew awareness and not a procedure. Flight attendant reported that the smell had subsided or cleared entirely. Minutes later; the right recirculation fan failed again; and then again regained function. I had the first officer (first officer) turn it off. Coincidently the flight attendant stated the smell had returned. I called [dispatch] and [maintenance] via sat phone to discuss. It seemed the odor was related to the right recirculation fan. Discussed continuing with the fan off with since again the smell went away when the fan was turned off.we contemplated continuing in this condition and were leaning towards that since the smell appeared to be related to the operation of the right recirculation fan. [Dispatch] was working on new fuel burns with the fan off for the remainder of the flight when the flight attendant reported that the smell had returned and that some passengers were complaining about the smell and some were alarmed. We still had no fumes in the cockpit. We decided to drop into [a nearby alternate].[dispatch] was still on the phone when decision was made. He sent us landing data. We performed the QRH for smoke; fire; fumes. We did not don the O2 masks due to the clean air conditions in the cockpit. I felt it would have been no help and perhaps a distraction. The O2 masks were out and ready and goggles were within reach should they be needed.fas were briefed. I told them until further notice it would be a normal landing. I told them to disregard the sterile light should conditions change for the worse. At that point we could have expedited and prepared for evacuation. The fumes were not causing breathing issues and there was no visible smoke. I thought a normal preparation and landing was appropriate for the actual situation. We accomplished all of our checklists; normal and abnormal; while losing altitude and being vectored.overweight landing was smooth. Local maintenance was fully debriefed on the landing and I filled out the smoke/fumes questionnaire with the assistance of the lead flight attendant. FAA met [us] and asked about any hazmat on board. There was none boarded and I told him as such. No other questions or interaction with FAA. Reps from the [company] also greeted us. Very supportive in offering any assistance. When we opened the cockpit door we could smell the acrid odor. Maintenance was able to smell it and got right to trying to identify it. I later got calls to discuss and answer any questions. All parties seemed satisfied. Aircraft swap occurred and we took off hours later.

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Original NASA ASRS Text

Title: B757 Captain reported diverting to an alternate airport after a Flight Attendant noticed an electrical smell in the cabin that was probably due to a recirculation fan anomaly.

Narrative: During cruise; Flight Attendants (FA) notified me of an acrid and electrical smell in the forward cabin. No fumes observed in cockpit. Coincidently the R recirculation fan momentarily failed and returned to functioning status with no crew interaction. QRH for recirculation fan is a crew awareness and not a procedure. FA reported that the smell had subsided or cleared entirely. Minutes later; the R recirculation fan failed again; and then again regained function. I had the First Officer (FO) turn it off. Coincidently the FA stated the smell had returned. I called [Dispatch] and [Maintenance] via sat phone to discuss. It seemed the odor was related to the R recirculation fan. Discussed continuing with the fan off with since again the smell went away when the fan was turned off.We contemplated continuing in this condition and were leaning towards that since the smell appeared to be related to the operation of the R recirculation fan. [Dispatch] was working on new fuel burns with the fan off for the remainder of the flight when the FA reported that the smell had returned and that some passengers were complaining about the smell and some were alarmed. We still had no fumes in the cockpit. We decided to drop into [a nearby alternate].[Dispatch] was still on the phone when decision was made. He sent us landing data. We performed the QRH for Smoke; Fire; Fumes. We did not don the O2 masks due to the clean air conditions in the cockpit. I felt it would have been no help and perhaps a distraction. The O2 masks were out and ready and goggles were within reach should they be needed.FAs were briefed. I told them until further notice it would be a normal landing. I told them to disregard the Sterile light should conditions change for the worse. At that point we could have expedited and prepared for evacuation. The fumes were not causing breathing issues and there was no visible smoke. I thought a normal preparation and landing was appropriate for the actual situation. We accomplished all of our checklists; normal and abnormal; while losing altitude and being vectored.Overweight landing was smooth. Local Maintenance was fully debriefed on the landing and I filled out the smoke/fumes questionnaire with the assistance of the lead FA. FAA met [us] and asked about any hazmat on board. There was none boarded and I told him as such. No other questions or interaction with FAA. Reps from the [company] also greeted us. Very supportive in offering any assistance. When we opened the cockpit door we could smell the acrid odor. Maintenance was able to smell it and got right to trying to identify it. I later got calls to discuss and answer any questions. All parties seemed satisfied. Aircraft swap occurred and we took off hours later.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.