Chungmuro Station on Subway Line No. 4 is crowded with commuters on April 8. (Yonhap) Four smoke incidents involving portable power banks were reported on Seoul subway trains over the past two months, prompting Seoul Metro to urge passengers to take extra care when carrying and charging lithium-ion batteries.According to Seoul Metro, all four incidents involved power banks carried by passengers. No injuries were reported, as emergency measures were taken at nearby stations before the situation escalated into fires.The first incident occurred on April 27 aboard a Line 3 train bound for Ogeum, when smoke began rising from a power bank inside a passenger’s bag, prompting an emergency evacuation.Three similar incidents followed at roughly one-week intervals. Smoke was reported from a passenger’s portable battery at Express Bus Terminal Station on May 12, at Sillim Station on May 18 and at Seoul Station on May 26.The latest cases follow similar incidents reported last year. Smoke was detected from a battery carried by a passenger aboard a Line 4 train, requiring emergency action at Ichon Station.In another case, smoke from an electric scooter battery carried by a passenger on the platform at Hapjeong Station caused Line 2 and Line 6 trains to temporarily bypass the station.Seoul Metro said lithium-ion batteries can overheat or catch fire when damaged, exposed to heat or charged improperly.The operator urged passengers to use certified chargers, avoid leaving devices charging unattended for long periods and refrain from storing batteries in hot or humid environments.Batteries that are swollen, damaged or deformed should be replaced immediately, it said.In the event of smoke or fire on a train, Seoul Metro advised passengers not to activate emergency door-opening devices. Instead, passengers should move to another car away from the affected area and notify train staff using onboard emergency communication systems.To strengthen emergency preparedness, Seoul Metro said it has equipped all stations under its jurisdiction with water tanks designed to cool overheated batteries.Specialized response equipment, including heat-resistant gloves and thermal tongs, has also been deployed to enable rapid initial responses to battery fires.