According to researchers at Drexel University, U.S, it will take up to 1,000 plants per square meter of floor to clean the air more efficiently than a ventilation system.
The research which was published earlier this week (November 6) in the Journal of Exposure Science and Environmental Epidemiology, reviewed dozens of studies that span over the course of 30 years in order to analyse the improvements to indoor air pollution made by potted plants.
According to the researchers, the myth around the benefits of potted plants began in 1989 when NASA declared that plants could remove cancer-causing chemicals from the air.
This experiment was conducted in a sealed chamber in a lab, an environment that has little in common with a house or an office.
The researchers decided to take data from various studies on indoor air pollution that were conducted in a sealed chamber and calculate the clean air delivery rate (CADR), the standard metric for studying the impact of air purifiers.
Through this calculation, for almost all of the studies, the researchers found that the rate at which plants removed volatile organic compounds (VOC) in a chamber was slower than the standard rate of air exchange in a building.
Building ventilation systems can, therefore, dilute concentrations of VOC much faster than plants can extract them from the air
The researchers said that this proves that the overall effects of plants on indoor air pollution are irrelevant.
According to the researchers, it would take between 100 and 1,000 plants per square meter of floor spaces to compete with the air cleaning capacity of a building’s air handling system or even just a couple of open windows in a house.
Micheal Waring, an associate professor of architectural and environmental engineering in Drexelâ€™s college of engineering said: â€˜This has been a common misconception for some time.â€™
‘Plants are great, but they donâ€™t actually clean indoor air quality enough to have an effect on the air quality of the building.â€™
â€˜The CADR is the standard metric used for the scientific study of the impacts of air purifiers on indoor environments, but many of the researchers conducting these studies were not looking at them from an environmental engineering perspective and did not understand how building air exchange rates interplay with the plants to affect indoor air quality.â€™
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