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The ability of indoor plants to improve air quality is greatly exaggerated.

Washington: Contrary to the common belief that indoor plants are known to improve air quality, a new finding has stated the opposite! While they may help improve the space of a home or office, their ability to improve air quality is greatly exaggerated, according to the study published in the Journal of Exposure Science and Environmental Epidemiology.

"This has been a common misconception for some time. Plants are great, but they don't actually clean the indoor air fast enough to affect the air quality of your home or office," said Michael Waring, PhD, associate professor of architectural engineering. and environmental research at the Drexel College of Engineering.

The researchers reviewed a dozen studies, spanning 30 years of research, to draw their conclusions. Their central finding is that natural air exchange rates or indoor ventilation rates, such as homes and offices, dilute concentrations of volatile organic compounds – the air pollution that plants are supposed to clean – much faster than plants can. extract them from the air.

The high-profile experiment that seemed to create the myth of houseplants as air purifiers took place in 1989, when NASA, looking for ways to clean air in space stations, stated that plants could be used to remove chemicals that cause airborne space. air cancer. But the problem with this experiment, and the like, is that they were conducted in a sealed chamber in a lab – a contained environment that has little in common with a home or office.

"Typical for these studies, a potted plant was placed in a sealed chamber (usually with a cubic volume or smaller), in which a single VOC was injected and its decay tracked over many hours or days," the researchers wrote. . Data from the current study of plant pot volumes researches a step further, using them to calculate a measurement called "clean air supply rate" or "CADR".

They were able to do this calculation for almost every study and what they found in all cases was that the rate at which plants dissipated VOCs in a chamber was orders of magnitude slower than the standard rate of air exchange in a chamber. building – therefore proving that the overall effect of plants on indoor air quality is irrelevant.

"CADR is the standard metric used for the scientific study of the impacts of indoor air purifiers, but many of the researchers who conducted them were not looking at them from an environmental engineering standpoint and did not understand how the exchange rates of air purifiers. air interact with plants affect indoor air quality, "said Waring.

Many of these studies have shown a reduction in the concentration of volatile organic compounds over time, which is probably why people have seized them to extol the air-purifying virtues of plants. But, according to the findings of the current study, it would take between 10 and 1,000 plants per square meter of floor space to compete with the air cleanliness of a building's air handling system or even with some windows open in a building. home.

"This is certainly an example of how scientific discoveries can be misleading or misinterpreted over time. But it is also a great example of how scientific research must continually re-examine and question findings to get closer to the basic truth of understanding what really is happening all around us. "Waring said.

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