With many recent reports of air conditioner fires that were unrelated to product defects, product safety experts are calling on consumers to make sure the environments around air conditioners are maintained appropriately, mindful that their use will increase with the approaching summer season.

According to the National Institute of Technology and Evaluation (NITE), a total of 345 air conditioner accidents were reported between fiscal 2021 and 2025, out of which 322 〞 over 90% 〞 were fires. Seven people died and 33 were injured due to air conditioner accidents during the period.

Among the 345 accidents, 152 cases were not caused by the products themselves but by external factors 〞 such as the spread of fires that occurred near air conditioners installed indoors or condenser units installed outdoors.

One condenser unit installed outdoors caught alight in Miyagi Prefecture in 2022. The unit was covered by a plastic sheet, and two plastic bottles containing water had been placed on it to prevent the sheet from being blown away. It was sunny on the day of the incident, and it is believed that the bottles ignited the fire by focusing sunlight onto a single point like a magnifying glass.

Another case in Tokyo in 2024 involved an air conditioner fire caused by loose wires, after a user apparently stripped insulation from the power cord for the unit, twisted the live wire and connected it with another cable.

Air conditioner manuals say users should not modify cords or connections. NITE said people must consult certified technicians when installing air conditioners.

The institute also noted the risk of fires from cigarettes not being properly extinguished, and warned users not to leave items like ashtrays or flammable material such as garbage bags, cardboard boxes or newspapers near air conditioner condenser units.

Such materials can also attract animals and insects that might infest the units and damage cables, it said.

Translated by The Japan Times