Shocker: Houseplants Don’t Clean the Air

The shocking truth is that for a normal 140 m² house or office (1,500 ft²), you’d need 680 houseplants or five per square metre to achieve the same air flow as opening a couple of windows, avert the environmental engineers from Philadelphia’s Drexel University.  “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,” says Michael Waring. 

The NASA studies on indoor pollution done in 1989 recommends 15 or 18 plants in 6- to 8-inch diameter containers to clean the air in an average 1,800 square foot house. That’s roughly one plant per 100 square feet of floor space. 

However, a home or office is not a sealed chamber. Air is constantly being exchanged with outside, as environmental engineers are well aware. In fact, they have a means of measuring such, termed clean air delivery rates (CADR). Other researchers have not taken these into consideration, say the latest study authors.

As for the list of alleged houseplants, those originally tested in the NASA study appear to have been added to at whim of supporters of the practice. And even in the original tests, not every plant was found to be totally effective at removing cancer-causing pollutants.

Want clean air? Just open a window, suggests Carly Cassella. During a northern winter? Or anytime in most big cities? Perhaps a commercial air purifier is the answer. But it won’t make you feel happier or more productive as will one or a positive rainforest of houseplants. As Michelle Dickinson suggests in The New Zealand Herald, “Admire them, talk to them” but don’t expect them to absorb pollutants.