Narrative:

After arrival at the gate; while completing post flight terminating duties; we had deplaned approximately the first 8 rows when I could hear from the cabin that there was smoke coming from somewhere. A strong odor of electrical smoke just hit us as well. Immediately I left the cockpit to access the situation and discovered that a male passenger had a backpack which was 'smoking' and he had just entered the jetway. The gentleman had emptied his small backpack on the floor of the jetway and was seeking the source. Passengers continued to deplane around us and were anxious to leave the aircraft since there was a smell and we were also 45 minutes late. I could see that the situation was not escalating and no danger seemed to exist; but as a precaution the operations agent had a ramp agent bring up a fire extinguisher while an F/a [flight attendant] retrieved the containment bag from the cabin. After investigating the issue with our passenger; I feel certain that it was the spare battery he had in his bag; and when the bag caught on an armrest it jostled the contents to where the battery terminals came in contact with something that caused it to discharge at a fast rate. Sometime; as he deplaned the contact was lost and the source of heat removed. His other items (laptop and various electronics) had evidence of charring. The carpet in the jetway had a melted spot on it and the aircraft seat bottom cushion he briefly placed his bag on had an 8 square inch area of soot. No damage was done to the aircraft with the smoke smell diminishing quickly in the absence of its source. The seat cushion was able to be cleaned off. The time from first smoke indication to situation under control was less than three minutes. The quick actions of the entire crew helped this from escalating into an incident. I commend our three F/a's for their quick actions. My first officer [first officer] maned the cockpit in case we had to issue evacuation orders. I know very well that ir's [incident reports] should be factual and without emotional but ped's [personal electronic devices] pose a huge threat on each flight and it will not be a matter of if; but when; life will be lost as we have no control over what is brought onboard. Please; as you are reading this in a comfortable office; place yourself in the situation of being enclosed in a tube several miles high and not being able to get on the ground anytime soon. Also please look up ir xxxxxx (date) and consider had this been a deliberate attack on the flight deck what the consequences would have been. The bar on the cockpit floor of the maximum must be implemented on every plane we have immediately. Management must trust and listen to the front line employees. They are the eyes and ears of our operation; but are most often overlooked as the valuable resource they are. This incident could have had grave consequences; had a bad actor decided to place an overheated device like this under the cockpit door. Only the maximum has protection to help prevent this and it is inexcusable to not retrofit the fleet. Since we do not offer usb charging ports at passenger seats it is inevitable that our passengers will rely on portable batteries to recharge their devices. Many of these are inferior products that have no place on any aircraft. As mentioned above it is not a matter of if but when. I have no idea how we can educate the flying public on what is safe to transport and how to do so. Just glad this did not occur half way over the pacific with a cabin full of fumes or possible fire/explosion.

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Original NASA ASRS Text

Title: B737-700 Captain reported during deplaning a carry-on backpack ignited and began to emit smoke. Fire hazard was quickly handled by flight crew with the Flight Attendant assistance in the jet bridge. The fire was caused by spare loose Lithium Ion batteries.

Narrative: After arrival at the gate; while completing post flight terminating duties; we had deplaned approximately the first 8 rows when I could hear from the cabin that there was smoke coming from somewhere. A strong odor of electrical smoke just hit us as well. Immediately I left the cockpit to access the situation and discovered that a male passenger had a backpack which was 'smoking' and he had just entered the jetway. The gentleman had emptied his small backpack on the floor of the jetway and was seeking the source. Passengers continued to deplane around us and were anxious to leave the aircraft since there was a smell and we were also 45 minutes late. I could see that the situation was not escalating and no danger seemed to exist; but as a precaution the Operations Agent had a Ramp Agent bring up a fire extinguisher while an F/A [Flight Attendant] retrieved the containment bag from the cabin. After investigating the issue with our Passenger; I feel certain that it was the spare battery he had in his bag; and when the bag caught on an armrest it jostled the contents to where the battery terminals came in contact with something that caused it to discharge at a fast rate. Sometime; as he deplaned the contact was lost and the source of heat removed. His other items (laptop and various electronics) had evidence of charring. The carpet in the jetway had a melted spot on it and the aircraft seat bottom cushion he briefly placed his bag on had an 8 square inch area of soot. No damage was done to the aircraft with the smoke smell diminishing quickly in the absence of its source. The seat cushion was able to be cleaned off. The time from first smoke indication to situation under control was less than three minutes. The quick actions of the entire crew helped this from escalating into an incident. I commend our three F/A's for their quick actions. My F/O [First Officer] maned the cockpit in case we had to issue evacuation orders. I know very well that IR's [Incident Reports] should be factual and without emotional but PED's [Personal Electronic Devices] pose a huge threat on each flight and it will not be a matter of if; but when; life will be lost as we have no control over what is brought onboard. Please; as you are reading this in a comfortable office; place yourself in the situation of being enclosed in a tube several miles high and not being able to get on the ground anytime soon. Also please look up IR XXXXXX (date) and consider had this been a deliberate attack on the flight deck what the consequences would have been. The bar on the cockpit floor of the MAX must be implemented on every plane we have immediately. Management must trust and listen to the front line employees. They are the eyes and ears of our operation; but are most often overlooked as the valuable resource they are. This incident could have had grave consequences; had a bad actor decided to place an overheated device like this under the cockpit door. Only the MAX has protection to help prevent this and it is inexcusable to not retrofit the fleet. Since we do not offer USB charging ports at passenger seats it is inevitable that our passengers will rely on portable batteries to recharge their devices. Many of these are inferior products that have no place on any aircraft. As mentioned above it is not a matter of if but when. I have no idea how we can educate the flying public on what is safe to transport and how to do so. Just glad this did not occur half way over the Pacific with a cabin full of fumes or possible fire/explosion.

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.