Indoor Plants: Do They Really Purify the Air?

The growing use of indoor plants is best indicated by January 10th – National Houseplant Appreciation Day. This is a day to celebrate the benefits and joys that houseplants bring. But with growing numbers of households adding indoor plants, it’s important to correct some underlying misconceptions. Mainly whether or not indoor plants really clean indoor air. Those who support the use of indoor plants for air purification point to a famous NASA experiment.

The NASA Experiment

In 1989, NASA released a report titled, “Interior Landscape Plants for Indoor Air Pollution Abatement.” Through a series of experiments, they tested to see whether indoor plants impacted indoor air pollution. They used a variety of plants, including Gerbera daisies, English ivy, Peace lilies, and bamboo palms, among others. They used sealed experiment chambers where plants were placed inside, in order to monitor the levels of airborne chemicals before and after. Ultimately, they found that various houseplants removed benzene, TCE, and formaldehyde—harmful volatile organic compounds (VOCs)—from the air.

Push Back?

Although the NASA findings themselves are not argued, several scientists and professors have entered the debate to clarify the narrative that has since taken a life of its own.

Luz Claudio, a professor of environmental medicine and public health at the Icahn School of Medicine at Mount Sinai, states, “There are no definitive studies to show that having indoor plants can significantly increase the air quality in the home to improve health in a measurable way.”

A 2009 study tested 28 different plant species to find the highest efficiencies for removing VOCs (specifically benzene, toluene, octane, TCE and a-pinene) from the surrounding air. However, their conclusion is couched in the experimental conditions – sealed glass containers in a laboratory environment. Stanley Kays, one of the scientists from the above study, notes the important characteristics of a laboratory experiment and how to carefully extrapolate findings to a real-world environment. Plants in laboratory settings are often superior in quality due to optimal growing conditions, which impact photosynthesis processes and therefore air purifying capabilities. He notes the difference between a sealed container and an open home – whereby outdoor air and indoor air is readily exchanged.

Although Kays supports the various benefits of household plants, especially regarding improved mood and increased energy levels, he admits, “At this time, it doesn’t look like plants sitting passively in a house are effective enough to make a major contribution to purifying indoor air.”

Indoor Plants as Support

Through a process of photosynthesis, plants convert carbon dioxide into oxygen. Thus, it is indisputable that plants are essential to human life. Nonetheless, the current dialogue surrounding indoor plants and air purification has spun from the initial scientific findings of 1989.

The original NASA report itself concludes with the following statement:

“Activated carbon filters containing fans have the capacity for rapidly filtering large volumes of polluted air and should be considered an integral part of any plan using houseplants for solving indoor air pollution problems.” (page 18)

The study itself recommends a supportive role. Indoor plants – like all plants – increase oxygen indoors and absorb certain VOCs, like benzene and formaldehyde, in laboratory settings. But whether indoor plants make a noticeable impact to indoor air quality is more complicated. Indoor plants can serve multiple functions for your home, but they should not be substituted for activated carbon filters and air purifiers.