Don't count on potted plants to keep your home's air clean.

Dispelling a common belief, researchers at Drexel University in Philadelphia found that natural ventilation does a far better job than houseplants in maintaining air quality in homes and offices.

"This has been a common misconception for some time. Plants are great, but they don't actually clean indoor air quickly enough to have an effect on the air quality of your home or office environment," said Michael Waring, head of Drexel's indoor environment research group.

His team analyzed dozens of studies conducted over 30 years. Their findings were published online Nov. 6 in the Journal of Exposure Science and Environmental Epidemiology.

The researchers said air-exchange rates indoors — either natural or from ventilation — dilute concentrations of volatile organic compounds (VOCs) far faster than plants can pull them from the air. VOCs are the air pollutants that plants are supposed to clean.

Many of the studies reviewed did find that plants reduced concentrations of VOCs over time. This likely led to the widespread belief that plants can purify indoor air, the study authors said.

But it would take between 10 and 1,000 plants per square meter of floor space to match the air cleaning capacity of a building's air-handling system or even just a couple of open windows in a house, the investigators found.

"This is certainly an example of how scientific findings can be misleading or misinterpreted over time," Waring said in a university news release.

"But it's also a great example of how scientific research should continually reexamine and question findings to get closer to the ground truth of understanding what's actually happening around us," he added.