How Many Houseplants are Needed to Clean the Air in Your Room?

One thousand. That’s how many houseplants are needed to clean the air in your home—that’s 1,000 per room. Many people offer up the argument that houseplants can clean the air in your home, making it a healthier and safer place for you and your family. The claim is actually based on science, but some liberties may have been taken when making those claims.

The rumour started with a 1989 NASA study that seemed to report that having houseplants in your home and office could help clean the air of airborne toxins, acting like natural indoor purifiers. New research, however, indicates that houseplants actually have very little impact on indoor air quality. The NASA study pointed to ficus, daisies, mums, and other plants as being particularly capable of pulling volatile organic compounds, or VOCs, like benzene and formaldehyde from small areas, like a space shuttle. That led to more studies showed similar effects.

“The main issue with the NASA study—and other chamber studies of potted plants and VOCs—isn’t that the data are incorrect,” says Michael Waring, Ph.D., an associate professor of environmental engineering at Drexler University. “Rather, the interpretation of the data and its application to indoor air cleaning are flawed.” Part of the problem is that while the studies were conducted in airtight environments, we live in ventilated spaces, meaning the air is constantly circulated.

The plants can’t keep up enough to make a difference. The studies also only focused on one or two chemicals at a time. We should be so lucky if our air actually only had one or two problems at a time.

That’s not to say that the plants don’t have an effect, it’s just not much of one. To really get the air-cleansing benefit of plants to work, you’d need a jungle filling your home or office. For a 10 foot by 10-foot room with an 8-foot ceiling, you would need 1,000 plants to match what a standard ventilation system can do.

But while the plants may not clean the air as you thought, they do dress up your room and can help create a more relaxing environment. So don’t be afraid to add a little green, just be realistic in your expectations of what that green will do.

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