Narrative:

During the boarding process I was made aware that the B flight attendant at the overwing exit; along with several passengers in his immediate vicinity; smelled a hot; rubbery; somewhat plastic burning smell. We stopped boarding and it was apparent we did not have a worsening situation by the demeanor of the passengers in the cabin. I could not see or smell anything untoward from the forward galley. I then went to mid-cabin myself to see what; if anything; I could smell and talk to any passengers who smelt the smell. While I could not smell anything; it was clear in talking to several passengers the B flight attendant had accurately described the smell; but it must have been very localized; as when talking with the deadheading captain; about seven rows behind the exit; he had not smelled anything. At this point; we had checked for obvious sources such as lights and overhead bags and nothing was noted. I did not believe it to be the ground air source as the smell was so localized. I made a PA to the passengers informing them we had had an unknown odor reported while boarding and would need a little while to talk with maintenance. We were just about to call dispatch and maintenance control to discuss the writeup (as clearly this would need a maintenance inspection at the very least with an unknown heat source/burning smell); when the a flight attendant came forward to inform me the source had been located. A passenger; seated right next to the B flight attendant at the overwing exit; had multiple e-cigarettes and one battery shorted out; overheating another. I had them bring the passenger to the flight deck and I talked with him. We had him bring his backpack (which was under the seat in front of him) to the jetway and the B flight attendant was able to; without any doubt; confirm the smell was exactly the same. The vapes were wrapped in a large ziploc back and the bag was hot to the touch. The operations agent asked the passenger if he had any more vape materials in his backpack and he did. The operations agent then asked if he could remove all those and if he would consent to a voluntary search of his back; which he agreed to. Other than the vape materials he showed us; there were no others. We had the passenger with the vape materials remain in the jetway and first officer and I consulted our manuals. We found some reference to efb battery thermal runaway issues but nothing for passenger luggage overheating issues; other than the general inflight QRH guidance. We did find a reference to it being a hazmat reportable incident. I made another PA to the passengers informing them that the source of the odor had been located; and what it was. I also told them it would require some additional paperwork and to give us fifteen minutes to resolve the issue. I consulted with my first officer and the flight attendants and we were all in agreement it was safe and appropriate to continue the flight. I then called dispatch and the chief pilot on call and they both; along with the sod; agreed it was appropriate to continue boarding and dispatch the flight. As we had burned below minimum planned fuel; we also amended the dispatch release to allow legal dispatch without a further delay to load more fuel. We allowed the offending passenger; sans vape materials to re-board and boarded the remaining passengers. I made a PA to all the passengers thanking them for their patience and understanding and the rest of the flight was uneventful. The passenger with the vape material; other than being disappointed that the vapes that didn't short out could not travel with him; was most understanding and cooperative. My first officer; all three flight attendants and isp operations acted in an exemplary manner throughout the whole event. All the passengers were most understanding throughout the event too. Thank you for your time to read this report.

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Original NASA ASRS Text

Title: B737-700 Captain reported Flight Attendant notification of hot burning plastic in passenger cabin during passenger boarding.

Narrative: During the boarding process I was made aware that the B Flight Attendant at the overwing exit; along with several passengers in his immediate vicinity; smelled a hot; rubbery; somewhat plastic burning smell. We stopped boarding and it was apparent we did not have a worsening situation by the demeanor of the passengers in the cabin. I could not see or smell anything untoward from the forward galley. I then went to mid-cabin myself to see what; if anything; I could smell and talk to any passengers who smelt the smell. While I could not smell anything; it was clear in talking to several passengers the B Flight Attendant had accurately described the smell; but it must have been very localized; as when talking with the deadheading Captain; about seven rows behind the exit; he had not smelled anything. At this point; we had checked for obvious sources such as lights and overhead bags and nothing was noted. I did not believe it to be the ground air source as the smell was so localized. I made a PA to the passengers informing them we had had an unknown odor reported while boarding and would need a little while to talk with Maintenance. We were just about to call Dispatch and Maintenance Control to discuss the writeup (as clearly this would need a maintenance inspection at the very least with an unknown heat source/burning smell); when the A Flight Attendant came forward to inform me the source had been located. A passenger; seated right next to the B flight attendant at the overwing exit; had multiple e-cigarettes and one battery shorted out; overheating another. I had them bring the passenger to the flight deck and I talked with him. We had him bring his backpack (which was under the seat in front of him) to the jetway and the B Flight Attendant was able to; without any doubt; confirm the smell was exactly the same. The vapes were wrapped in a large Ziploc back and the bag was hot to the touch. The Operations Agent asked the passenger if he had any more vape materials in his backpack and he did. The Operations Agent then asked if he could remove all those and if he would consent to a voluntary search of his back; which he agreed to. Other than the Vape materials he showed us; there were no others. We had the passenger with the vape materials remain in the jetway and First Officer and I consulted our manuals. We found some reference to EFB battery thermal runaway issues but nothing for passenger luggage overheating issues; other than the general inflight QRH guidance. We did find a reference to it being a HAZMAT reportable incident. I made another PA to the passengers informing them that the source of the odor had been located; and what it was. I also told them it would require some additional paperwork and to give us fifteen minutes to resolve the issue. I consulted with my First Officer and the Flight Attendants and we were all in agreement it was safe and appropriate to continue the flight. I then called Dispatch and the Chief Pilot on Call and they both; along with the SOD; agreed it was appropriate to continue boarding and dispatch the flight. As we had burned below minimum planned fuel; we also amended the Dispatch Release to allow legal dispatch without a further delay to load more fuel. We allowed the offending passenger; sans vape materials to re-board and boarded the remaining passengers. I made a PA to all the passengers thanking them for their patience and understanding and the rest of the flight was uneventful. The passenger with the vape material; other than being disappointed that the vapes that didn't short out could not travel with him; was most understanding and cooperative. My First Officer; all three Flight Attendants and ISP Operations acted in an exemplary manner throughout the whole event. All the passengers were most understanding throughout the event too. Thank you for your time to read this report.

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.