The idea is that, by combining these measurements into a single metric, consumers are less likely to be misled by, for instance, an air filter that is incredibly efficient at removing toxins, but only for a small amount of air. The industry’s standard metric for the effectiveness of air filters is clean air delivery rate, or CADR, which combines separate measures for airflow and how efficiently particles are removed. Richard Corsi, dean of the College of Engineering at UC Davis, also takes umbrage with what he calls these “little glass chamber studies.” The issue, he says, is that to get their results, researchers exaggerate the amount of air that would ever flow over a plant in normal conditions.

In 2019, however, researchers at Drexel University concluded that, in order for the effects measured in these chamber experiments to be reproduced at any livable scale, and to even match the rate of toxin removal already achieved by just opening a window, you’d need anywhere between 10 and 1,000 plants per square meter. This has not stopped many researchers since from conducting almost exactly the same experiment. Putting a plant in a sealed chamber, blowing pollutants over it for multiple hours (or days), and then recording the results, the researchers admitted, was not an accurate replication of normal houseplant conditions. The resulting Clean Air Study suggested that, yes, houseplants could absorb certain pollutants-including VOCs like benzene, formaldehyde, and trichloroethylene. Less touted was the fact that these results mostly could not be applied to the houses these plants are often placed in.

Much of the support for these marketing efforts stems from 1989, when NASA worked with the Associated Landscape Contractors of America to assess the ability of houseplants to remove toxins from the air.

Instagramstorysaver