“It’s such an alluring and enticing idea,” Elliot Gall, a Portland State University professor, told me. “But the scientific literature shows that indoor houseplants—as would be typically implemented in a person’s home—do very little to clean the air.”
“My view is even harsher than that,” Michael Waring, an engineering professor at Drexel University, told me. “I do not think that houseplants clean the air.”
“A resounding ‘no,’” agreed Richard Corsi, a longtime air-pollution researcher, in an email. Houseplants do not clean the air “any more than an old pair of socks or baseball cap that I would hang on the wall.”
Why the confusion? Big Succulent isn’t lying to you, though at this point the houseplant industry is cherry-picking data. But for plants to actually improve the air, even in a compact apartment, you’d need a concentration of houseplants that only the most dedicated plant lovers can actually achieve.
Important fact that wasn't addressed by either party: ozone synthesis and diffusion are severely hindered by humidity, for similar reasons as to why experiments with electrostatics (e.g. rubbed amber lifting confetti) work better in dry air. Dry air also causes stomata on plant leaves to rapidly shut close, which naturally would reduce their potential for air exchange.