Your Houseplants Aren't Actually Improving the Air Quality in Your Home

Potted house plants are commonly thought to purify indoor air, often finding themselves in homes and offices for this reason. But scientists now believe their powers might be wildly overestimated.

Plants are known to soak up volatile organic compounds (VOC), a type of indoor pollutant. But simply cracking open a few windows or fitting an air handling system in an office can clear the air faster than plants, according to researchers at Drexel University, Pennsylvania.

Depending on the size of the space, the researchers calculated it would take between 10 to 1,000 plants per square meter (10.7 square foot) of floor space to clean the air at the same level as an open window or specialized equipment.

As people in developed countries spend up to 90 percent of their time indoors, it is important to understand the sorts of pollutants we encounter in these enclosed spaces and find effective ways to combat them, the authors argued.

Co-author Michael Waring, associate professor of architectural and environmental engineering in Drexel's College of Engineering, told Newsweek: "We noticed that there was a common misconception on the internet that potted plants improve indoor air quality.

"Though many of us in the indoor air quality field had come to the conclusion that this assumption was not true, there was no definitive study in the literature that synthesized all the available chamber data and then demonstrated plants to be ineffective at VOC removal."

Waring told Newsweek he partly traced the overegged idea back to an oft-cited 1989 NASA study, which looked at how to purify the air of space stations. The research is deemed significant enough to have its own Wikipedia page.

For their study, published in the Journal of Exposure Science and Environmental Epidemiology, Waring and his doctoral student Bryan Cummings pored over 12 existing studies relating to indoor plants and air quality, conducted over the past three decades.

The researchers argue studies that suggest plants have cleansing powers don't relate to the home or office, as they were largely conducted in controlled lab environments, where plants were placed in sealed chambers for hours or days. In contrast, buildings are much bigger than such chambers, and VOCs are persistent in these settings, they said.

Using the data from the previous studies, the team worked out what is known as the "clean air delivery rate" of the respective plants, a measure of how well something can purify the air.

While plants appeared to reduce levels of VOCs, they weren't found to be as powerful as is sometimes claimed.

"The best way to achieve good indoor air quality is to remove any strong sources of pollution inside, ventilate well if the outdoor air is clean, and use effective air cleaning devices if they are available (e.g. a HEPA filter)," said Waring.

However, Waring said their potted plants could still have many benefits, even if they aren't cleaning the air—by boosting our psychological health, for example.