The study was conducted in a controlled environment-a sealed room with a volume of approximately 82.2 m³, located at the H. C. Ørsted Institute at the University of Copenhagen. FIGURE shows the setup room. The room was undisturbed during the study, and baseline conditions were recorded before air purifier activation. PM1 and PM2.5 concentrations were measured using time-stamped readings at regular intervals. Sensors were first placed 1 cm apart to correlate proximity and were intercalibrated according to the results. Three intercalibrated particulate matter sensors were used to count particle concentrations simultaneously. The locations of the sensors are highlighted by the red circles in FIGURE .