The National Fire Agency urged caution, saying that "illegal mixed refrigerants" for air conditioners distributed online and elsewhere can create a self-igniting substance inside outdoor units and lead to fires.
According to the National Fire Agency on the 2nd, production of the R-22 refrigerant used in older air conditioners was halted after 2023 due to ozone depletion concerns, and low-cost illegal mixed refrigerants that did not go through formal import procedures are being distributed through online marketplaces and direct overseas purchases.
There are many cases of mixing R-40 into R-22 cylinders for sale. R-40 was once used as a refrigerant but was phased out due to high toxicity and flammability. It is also a substance whose new use as a refrigerant was completely banned under the 1987 Montreal Protocol.
A tracking review of fires suspected to have been caused by air conditioner refrigerants over the past five years found a total of 36 cases. There was 1 case in 2022, 2 in 2023, 6 in 2024, 13 in 2025, and 14 as of July 2026, showing an annual upward trend.
As a result of a joint investigation by the National Fire Agency, the National Fire Research Institute, fire investigation agencies in Seoul and Gyeonggi, and the South Gyeongsang Fire Headquarters to identify the risks, it was confirmed that chloromethane contained in illegal mixed refrigerants reacts with aluminum components inside the outdoor unit to produce "trimethylaluminum."
Trimethylaluminum is classified as a Class 3 hazardous material under the Hazardous Materials Safety Control Act, self-igniting when exposed to air and reacting violently upon contact with water to create flammable substances. The National Fire Agency said that while systems operate normally when illegal mixed refrigerants are first charged, hazardous substances are generated during operation and can lead to fires when they later come into contact with air or moisture during removal or recharging.
In June this year, a man in his 70s was seriously injured in an explosion while injecting gas into an outdoor unit at a dwelling in Ganghwa, Incheon, and was airlifted by doctor helicopter.
In July, at a dwelling fire scene, a fire investigator collecting evidence suffered second-degree burns to both hands from sparks at the outdoor unit's refrigerant inlet.
The National Fire Agency warned that genuine refrigerants that have undergone formal customs clearance and quality inspections are safe, but illegal mixed refrigerants can lead to fires. It also advised: ▲ Be suspicious of refrigerants priced far below market rates ▲ Do not use companies that use refrigerant cylinders without quality certification marks ▲ Always use properly registered companies for installation, and, in the event of an accident, verify, record, and keep the installer's personal information to determine liability.
The National Fire Agency plans to work with relevant ministries to review measures to block the import and online distribution of illegal mixed refrigerants and to issue consumer alerts. Ju Young-guk, director general of 119 Response at the National Fire Agency, said, "Illegal mixed refrigerants cannot be identified by the naked eye, making it difficult for users to recognize the risk," and added, "We will continue to monitor the occurrence of fires with the relevant ministries and promptly inform the public of any additional findings."