Effects of non-thermal plasma on disinfection of indoor air and reduction of particulate matter.

Indoor airborne microorganisms and particulate matter (PM) are associated with respiratory infections and non-communicable diseases, posing a significant public health concern. This study evaluated the effectiveness of non-thermal plasma (NTP) for air disinfection and PM removal under real-world conditions. Chamber experiments were conducted using air artificially contaminated with PM, and reduction rates were compared between NTP and control groups. Field investigations were performed in an unoccupied classroom and a clinic during normal operation, and airborne bacterial concentrations, PM levels, and influence of human activities and environmental factors were evaluated. The results showed that a 30-min NTP treatment reduced approximately 90% of PM2.5 concentration in the chamber, after adjustment for natural decay. Under unoccupied conditions, airborne bacterial concentrations were significantly decreased after 90 min of NTP disinfection, when compared with no treatment. Under occupied conditions, although human activities increased bacterial and PM levels, both indicators declined with prolonged disinfection duration. The highest bacterial load occurred in the 1.1-2.1-µm particle-size fraction. Thus, controlling the number of occupants and minimizing unnecessary door opening during clinical procedures may enhance disinfection efficiency. Overall, NTP effectively inactivated airborne bacteria and removed PM, showing promising potential for improving indoor air quality and reducing airborne disease transmission risks.