Impacts of Portable Air Purifiers on the Oxidative Potential and Sources of Organic Matter in Indoor PM2.5

Organic matter (OM) is a major contributor to the oxidative potential (OP) of indoor PM_2.5. Portable air purifiers equipped with high-efficiency particulate air (HEPA) filters are known to effectively remove indoor PM_2.5 mass concentrations. However, their impacts on the OP and sources of indoor PM_2.5 OM and whether these impacts could further affect the OP of indoor PM_2.5 metals remain poorly understood. In a crossover trial, each of the 43 asthmatic children underwent a 2-week true filtration (HEPA + activated carbon [AC]) and sham filtration (no HEPA + no AC), with randomized order. PM_2.5 samples, simultaneously collected in participants’ bedrooms and outside their homes, were measured for mass concentration, composition, mass-normalized OP (OP_m, OP per mass), and volume-normalized OP (OP_v, OP_m × mass concentration). Compared to the sham filtration, indoor PM_2.5 OM mass was 34% lower, OP_m was 70% lower, and OP_v was 80% lower during true filtration. The reduction in OM OP_v was largely attributed to removing more reactive outdoor OM and indoor secondary OM. The change in OM composition also contributed to the reduced PM_2.5 metals’ OP_m. Our results suggest that indoor air purifiers with HEPA and AC filters efficiently reduce PM_2.5 OP_v by removing OM.

Little is known regarding how portable air purifiers affect the organic matter (OM) in indoor PM_2.5. This study presents evidence showing that portable air purifiers equipped with HEPA and AC filters can effectively remove the OM’s oxidative potential by removing its mass concentration and more reactive OM species.