Experimental assessment of the efficacy of portable air cleaners in mitigating respiratory droplet nuclei transmission

This study assesses the impact of portable air cleaners (PAC) on the spread of respiratory particles between two thermal manikins (infected and exposed) in a climate chamber. It explores three types of PAC, namely conventional (PAC1), table (PAC2) and personalized (PAC3) in various locations and operation modes. The particles were generated by an aerosol generator and introduced into the infected manikin's exhalation. The particle concentration at the exposed manikin's breathing zone was measured using an aerodynamic particle sizer. The results indicated that at low fan speed, PAC2 performed the best, followed by PAC1 and PAC3. Additionally, operating PAC units in turbo mode may not consistently mitigate exposure risk. It was found that after 60 minutes, PAC1 and PAC2 increased the intake fraction (IF) by 4.4 and 12.1 times, or decreased it by 30 and 12.8 times compared to when the PAC is turned off. These changes varied depending on their location in the climate chamber. Furthermore, with increased PAC operation time, the difference in IF between low and high fan speeds tended to become insignificant.