Effectiveness of plants for passive removal of particulate matter is low in the indoor environment

Particulate air pollution is a major health concern and is responsible for about one in nine premature deaths worldwide. Significant exposure to particulate matter (PM) may happen indoors because people spend a large fraction of their time inside buildings. Indoor plants have been suggested as a potential solution for removing PM; however, their effectiveness has not been well characterized. We quantified the ability of eleven different plant species to remove airborne PM through experiments conducted in an environmental chamber. By introducing PM into the chamber and measuring its removal rate with and without the plants, we estimated plants' deposition velocities and clean air delivery rates (CADRs). The average deposition velocities were 93 +/- 9 cm/h for the moss plant, between 29 +/- 3 cm/h to 37 +/- 4 cm/h for the needle-leaved plants, and between 1 +/- 2 cm/h to 13 +/- 2 cm/h for the broad-leaved plants. Their CADRs were between 0.002 +/- 0.004 m(3)/h to 0.084 +/- 0.009 m(3)/h, which were significantly lower than those of filter -based air purifiers (CADRs = 170-800 m(3)/h), meaning that passive plant systems cannot compete with con-ventional air purifiers. We also found that large quantities of plants would be required to achieve even modest reductions in indoor PM concentrations under real-world conditions, thus highlighting their limited role in controlling indoor PM levels.

Automated summary

Particulate air pollution is a global health concern, and this study finds that indoor plants are not effective in removing airborne particulate matter. The study quantified the deposition velocities and clean air delivery rates of different plant species and compared them with filter-based air purifiers. The results show that plant systems cannot compete with traditional air purifiers, and a large quantity of plants is required to achieve modest reductions in indoor PM concentrations.