Narrative:

We were approximately 18-20 min out. I noticed the cabin temperature was a bit cold and I turned the temp controller to about the 3 o'clock position to warm up the cabin. About a minute or two after that; the first officer (first officer) and I noticed a faint smell in the air. It was somewhere between a musty warm smell and an electrical insulation smell. It was not strong at all; and it in no way caused irritation to the eyes or lungs. Just then the flight attendant (flight attendant) called forward to report the same thing; as well as it being at bit warm air temp wise for passengers. While the first officer was talking to the flight attendant; I turned on the cockpit overhead white light to see if there was any 'pooling' of smoke in the top of the ceiling. Just as a hunch as the temp controller was the last thing adjusted; I felt the panel; cold to touch; and turned the control knob to full cold. I talked with the flight attendant and told her what we were experiencing; she said the same and said she was going to look in the cabin and lav. I told her we were going to look into things on our side. The first officer and I agreed that while this should be taken as a serious potential threat; that under the current circumstances and being inbound and close to our destination; that we had time to evaluate things further before a need to escalate our action and or needing to [advise ATC]. Within a few minutes of turning the heat knob down; the smell lessened and disappeared entirely. While we were pleased to see a result in our action; we were still vigilant that there could still be a problem unseen. We did not know this yet; but the temp control movement and resulting dissipation were entirely coincidental. The flight attendant called forward and told us that she had found the problem. As she made her way back in the cabin; a passenger alerted the flight attendant that she had a battery powered cell phone charging unit that had gotten very hot while actively charging her phone and was emitting a smell. The flight attendant took the unplugged unit and removed the aa batteries from the charger and then called us. I told her to hang on to the unit until we deplaned the aircraft. The smell was completely gone and we arrived without any further issue.post flight; I looked at the charger unit; and it looked like an extremely cheaply manufactured charging unit. There was no visible scorching or soot on the unit; but the open unit itself smelled exactly like what all 3 of us had smelled earlier. I talked to the passenger and thanked her profusely for immediately bringing it to the flight attendant attention; and had the unit returned to her. She said she was amazed how hot the unit got while in use; and that it had been a gift item. She said it would never be used again.I want to thank the passenger for stepping forward and helping us to avoid a potential aircraft smoke emergency situation; and highly praise the professionalism; calmness and excellent communication skills that the flight attendant demonstrated in handling this situation.maintenance was notified and agreed it was not an aircraft issue; but a faulty passenger electronic device issue.

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Original NASA ASRS Text

Title: CRJ Captain and Flight Attendant reported they noticed a faint burning odor which was traced to an overheating cell phone charger in the cabin.

Narrative: We were approximately 18-20 min out. I noticed the cabin temperature was a bit cold and I turned the temp controller to about the 3 o'clock position to warm up the cabin. About a minute or two after that; the First Officer (FO) and I noticed a faint smell in the air. It was somewhere between a musty warm smell and an electrical insulation smell. It was not strong at all; and it in no way caused irritation to the eyes or lungs. Just then the Flight Attendant (FA) called forward to report the same thing; as well as it being at bit warm air temp wise for passengers. While the FO was talking to the FA; I turned on the cockpit overhead white light to see if there was any 'pooling' of smoke in the top of the ceiling. Just as a hunch as the temp controller was the last thing adjusted; I felt the panel; cold to touch; and turned the control knob to full cold. I talked with the FA and told her what we were experiencing; she said the same and said she was going to look in the cabin and lav. I told her we were going to look into things on our side. The FO and I agreed that while this should be taken as a serious potential threat; that under the current circumstances and being inbound and close to our destination; that we had time to evaluate things further before a need to escalate our action and or needing to [advise ATC]. Within a few minutes of turning the heat knob down; the smell lessened and disappeared entirely. While we were pleased to see a result in our action; we were still vigilant that there could still be a problem unseen. We did not know this yet; but the temp control movement and resulting dissipation were entirely coincidental. The FA called forward and told us that she had found the problem. As she made her way back in the cabin; a passenger alerted the FA that she had a battery powered cell phone charging unit that had gotten very hot while actively charging her phone and was emitting a smell. The FA took the unplugged unit and removed the AA batteries from the charger and then called us. I told her to hang on to the unit until we deplaned the aircraft. The smell was completely gone and we arrived without any further issue.Post flight; I looked at the charger unit; and it looked like an EXTREMELY cheaply manufactured charging unit. There was no visible scorching or soot on the unit; but the open unit itself smelled exactly like what all 3 of us had smelled earlier. I talked to the passenger and thanked her profusely for immediately bringing it to the FA attention; and had the unit returned to her. She said she was amazed how hot the unit got while in use; and that it had been a gift item. She said it would never be used again.I want to thank the passenger for stepping forward and helping us to avoid a potential aircraft smoke emergency situation; and highly praise the professionalism; calmness and excellent communication skills that the FA demonstrated in handling this situation.Maintenance was notified and agreed it was not an aircraft issue; but a faulty passenger electronic device issue.

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.