Localized and Whole-Room Effects of Portable Air Filtration Units on Aerosol Particle Deposition and Concentration in a Classroom Environment

Recirculating portable air filtration (PAF) units may supplement existing building ventilation in classrooms and reduce disease transmission (e.g., COVID-19) via the direct aerosol route (i.e., direct inhalation of aerosol particles) and an indirect aerosol route (i.e., contact with the surface[s] where aerosol particles deposited). We systematically investigated how three PAF units impacted localized and whole-room surface deposition and particle concentrations within a classroom. Results revealed that peak concentrations were reduced by a factor of ~2.5 by the PAF units, leading to an approximate 33% reduction in average deposition velocities for horizontal surfaces >2.5 m from the aerosol source. PAF units can thus reduce suspended particle concentrations and deposition throughout a classroom space when properly positioned with respect to the location of the potential infection source(s) (e.g., where the largest group of students sit) and the room's predominant air distribution profile.