Houseplants have been previously shown to play a role in removing volatile organic compounds (benzene, formaldehyde, etc.) from indoor air. Houseplants also participate in removal of ozone from indoor environments and they do so more effectively with light, demonstrating a role beyond passive surface reactions. Researchers at the University of Arizona and Portland State University measured ozone deposition velocities in chambers with different species of common houseplants, and different light conditions. The calculated effectiveness for ozone removal under reasonable plant density (0.06 m2 of leaf surface per m3 of indoor volume) and typical light conditions ranges between 0.9% and 9%. Ozone removal efficiency increased by a factor of 2 to 5 (depending on species) under typical light conditions, compared to dark conditions. These results indicate a modest but not negligible effect of houseplants in reducing indoor ozone exposures.