Filter-free air purifier that reduces ultrafine particles being deployed in Korea’s public spaces

High-capacity filter-free ultrafine particle reduction technology is now being deployed in subways, schools, department stores, and other large public facilities, significantly improving the living environment for citizens.

The research team led by Dr. Hak Joon Kim, Principal Researcher at the Department of Urban Environment Research of the Korea Institute of Machinery & Materials (KIMM), has developed an eco-friendly air purification technology that reduces ultrafine particulate matters without the use of filters.

This state-of-the-art filter-free air purification system utilizes electrostatic force while minimizing ozone generation. By incorporating microfiber discharge electrodes and nonmetallic carbon plates, the system operates on low current yet removes more than 90% of ultrafine particles.

Additionally, it resolves the ozone issue inherent in conventional electrostatic methods, with an ozone emission level below 5 ppb—only one-tenth of the concentration found in general atmospheric conditions.

This technology is particularly effective in large spaces, offering efficient air purification without the drawbacks of traditional filter-based systems. Conventional air purifiers with filters suffer from decreased airflow due to clogging and require costly replacements.

In contrast, KIMM’s technology does not obstruct airflow, enabling the efficient purification of large volumes of air while eliminating the need for filter replacement, thus significantly reducing maintenance costs. In subway tunnel applications, the system does not require ducts, cutting manufacturing costs by more than 30%.

The technology has been successfully tested in subway tunnels at Seodaejeonnegeori Station, Oryong Station, and Jung-gu Office Station in Daejeon.

A filter-free air purifier designed for schools is also under CA certification process and is set for wider deployment, with pilot installations currently underway in an elementary school in Busan. Additionally, a pilot test in the HVAC system of a department store in Gyeonggi-do confirmed its fine particulate matter reduction effectiveness in commercial settings.

Principal Researcher Dr. Hak Joon Kim of KIMM stated, “This is the only technology that has fundamentally solved the ozone emission issue, which has long been a barrier to applying electrostatic methods indoors. Moreover, it is economically viable, reaching the break-even point within approximately three years after initial deployment.”

He added, “We are preparing for broader adoption through the Designation of Innovative Products, KC Certification for electrical safety, and CA Certification for air purifiers.”

KIMM President Seog-Hyeon Ryu commented, “Having researched electrostatic technology for over 20 years, KIMM has successfully developed a world-class ultrafine particle reduction technology, which has been validated through two years of pilot testing for both safety and effectiveness. Moving forward, we will expand its application to more public facilities, contributing to the health and well-being of the public.”

This research was conducted with support from a major project of KIMM, specifically the “Development of Core Mechanical Technologies for Smart Air Conditioning Systems to Control Infections and Pollution in the Post-Pandemic Era,” as well as the Ministry of Science and ICT’s “Development of a Low-Cost, Eco-Friendly Passive Ultrafine Dust Reduction Technology for Subways” project.

The technology’s innovation and excellence were recognized when it received the Frederick G. Cottrell Award at the 17th International Conference on Electrostatic Precipitation, 2024. It has since been transferred to air purifier companies for commercialization.