There are many reasons why you’d want to have house plants in your home or office. One benefit that often pops in people’s minds is that plants can help clean the indoor air. But is this true? An extensive review of decades of research says: No. The review, published this month in the Journal of Exposure Science & Environmental Epidemiology, examined a dozen studies that tested how potted plants might reduce indoor air pollutants over time.
You might be wondering: if it’s wrong, why is the common notion that house plants can purify the air in your home so popular? While the review article’s conclusion is clear — the title literally starts with, “Potted plants do not improve indoor air quality” – the studies it examined don’t have the same clarity. The answer boils down to differences in environment between the experiments and an actual office or home.
Past experiments involved potted plants being placed in small, sealed chambers. The scientists in these past studies then injected some volatile organic compound (VOC), a common class of indoor air pollutant, into the air and measured how much its concentration decreased over time. The experiments often lasted for hours or even days in order to detect a significant drop in air pollution. This does demonstrate that plants will remove pollutants from the air, but they do so incredibly slowly. That creates a problem when trying to extend these results to a house or an office space, which is what much of popular media has done with these past research findings. In the average American home or workplace, indoor air is actually replaced by air from outside in about an hour. That’s much faster than a plant can remove pollutants from a room.
To see how many plants you’d need to clean the indoor air, the review’s authors took the past observations and extended them to larger rooms and a larger number of plants. They found that even if you had a potted plant for almost every square foot of your home, the natural ventilation of the building would still being doing most of the work at getting rid of VOCs. (VOCs largely come from indoors in the first place, e.g. from cooking or using air fresheners). You’d need close to 10 plants per square foot before potted plants start cleaning the air at almost the same rate it’s removed via exchange with outdoor air!
The authors recommend future research efforts shift to environments that have the basic indoor process of exchanging air with the outside. Until then, if you want to better clear the air in your home, maybe just open a window.
Managing Correspondent: Jordan Wilkerson
Original Scientific Article:
Potted plants do not improve indoor air quality: a review and analysis of reported VOC removal efficiencies, Journal of Exposure Science & Environmental Epidemiology