According to a study published in Air Quality, Atmosphere & Health, common potted house plants can potentially reduce indoor air pollution significantly. The researchers even found that, in some conditions, plants may reduce nitrogen dioxide (NO2) by as much as 20%.
The study examines three houseplants: peace lily, corn plant and fern arum. Each was individually placed into a test chamber containing levels of NO2 comparable to an office located next to a busy road. Over the next hour, all of the plants were able to remove around half the NO2 in the chamber, regardless of whether the plant was in light or dark conditions, or if the soil was wet or dry.
The research team also found that for small- and medium-sized spaces (65 to 230 square feet) five houseplants would reduce NO2levels by around 20%. Larger spaces would simply need to add more plants.
"This is very different from the way indoor plants take up CO2 in our earlier work, which is strongly dependent on environmental factors such as night time or daytime, or soil water content," said lead researcher Dr. Christian Pfrang. "We don't think the plants are using the same process as they do for CO2 uptake, in which the gas is absorbed through stomata—tiny holes—in the leaves. There was no indication, even during longer experiments, that our plants released the NO2 back into the atmosphere, so there is likely a biological process taking place also involving the soil the plant grows in—but we don't yet know what that is."