Use of portable air purifiers as local exhaust ventilation during COVID-19

The purpose of this study was to determine if strategic placement of portable air purifiers would improve effectiveness of aerosol reduction in a space as compared to use as a general room air purifier. Two sizes of portable air purifiers were placed in two different positions intended to function similar to either a local exhaust ventilation hood or an air curtain to determine if strategic placement would lead to a reduction of particles in a worker's position at a desk in an office environment. Particle generators were used to introduce particulate into the air and personal aerosol monitors measured particles during each test condition. Results showed that when the medium room portable air purifiers used in this study were set to high, corresponding to 98 CFM, and placed near the breathing zone of each office worker with the unit's filter cover removed, the particle concentration was reduced 35% beyond the reduction that would be expected if the same units were placed on the floor behind the occupant's workstation. Results also indicated that the larger portable air purifier tested, positioned as close as reasonable to each occupant's breathing zone with the largest capture area possible (i.e., removing the unit's filter cover), delivers the best aerosol reduction performance. The authors concluded that as a layer of protection against transmission of airborne infectious organisms for office occupants, installing a portable air purifier, sized and operated similar to the units tested in this study on the desk 12 inches from the breathing zone of the worker, has the potential to reduce airborne particulate to a greater degree than if the same units were placed outside of the breathing zone, in the general cubicle area.