It is claimed that some houseplants purify the air of our homes. They are said to rid the indoor environment of pollutants, in turn improving our breathing, our mood, and our overall health. So, is it true, and, if so, how many plants does it take to clean a room?
The origin of the trend for air-purifying plants is a study by NASA that took place in the 1980s. Various plants were shown to clean the air within a sealed chamber that had similar conditions to the inside of a spaceship. After this pioneer research, further studies confirmed the ability of plants (such as weeping fig and peace lily) to improve air quality. The science was then applied to plants in the home, creating a huge demand for houseplants.
However, experts have doubted whether studies carried out in small sealed chambers that offer plants optimum growing conditions can be applied to the average home, which is ventilated and doesn't allow plants to photosynthesize at their peak. In 2020, a review in the Journal of Exposure Science and Environmental Epidemiology concluded that potted plants cannot improve indoor air quality as a result of the ventilation that most buildings possess, unless one had '10 to 1000 plants/m2 of a building's floor space'. This amount of houseplants would equal the ability of indoor-outdoor air flow to remove volatile organic compounds (VOCs) that pollute our homes via a manner of sources (from carpets to nail polish). In other words, using houseplants to purify the air is pointless if you regularly open your windows or have other forms of good ventilation.
This sentiment was echoed in 2021 in a study conducted at the University of Birmingham, which found that houseplants were only effective at reducing the pollutant nitrogen
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