[Reading Science] Air-Purifying Plants: Trust Them or Just Open the Window?

It is said that to purify the air in a household with four family members, you need to place flowerpots with 680 plants. Is the amount of flowerpots shown in the photo enough to achieve the effect?
[Photo by YouTube screen capture]

[Asia Economy Reporter Kim Jong-hwa] Social efforts to reduce fine dust are ongoing. Individuals are also exploring various ways to escape fine dust, such as installing air purifiers at home or bringing in more air-purifying plants.

In particular, the belief that growing air-purifying plants can cleanse indoor air remains strong. However, recent research highlighting that the effectiveness of air-purifying plants has been exaggerated and that opening windows actually provides better air purification has drawn attention.

In November last year, a research team led by Professor Michael Waring from Drexel University in Philadelphia, USA, reviewed 12 different papers published over the past 30 years on plant air purification in enclosed spaces and analyzed 196 experimental results. They revealed that the air purification rate of air-purifying plants is minimal compared to when windows are opened.

The research team demonstrated their findings using the unit called 'Clean Air Delivery Rate (CADR).' CADR represents the volume of clean air supplied per hour, measured in cubic meters per hour (㎥/h). A higher number indicates better air purification.

For air-purifying plants, the CADR was found to be very low at 0.023 ㎥/h. This means that in a 140㎡ area where a family of four lives, opening two windows yields the same CADR as having 680 potted plants, and in a typical building, the CADR from ventilation systems equals that of having 100 potted plants per square meter.

In other words, instead of placing 680 potted plants in a home for air purification or filling a 1㎡ space with 100 pots?making it difficult to move?it is better to simply open the windows wide.

The efficacy of air-purifying plants was first publicized in 1989 through experiments by NASA. NASA determined that air purification was crucial for astronauts living in sealed spacecraft for over a year to maintain their health. They conducted experiments by placing several air-purifying plants inside and announced that the plants proved effective.

The NASA research team placed plants in sealed spaces smaller than 1㎥ and injected volatile organic compounds (VOCs), which are carcinogens, to test how much the plants could remove. The results showed that plants removed up to 70% of VOCs within a day.

Areca Palm (right in the photo) and Lucky Bamboo, air-purifying plants selected by NASA in 1989. Photo by YouTube screenshot.

Based on these results, NASA reported that plants have excellent air-purifying effects and selected Areca palm and Dracaena as representative air-purifying plants. Consequently, the efficacy of air-purifying plants was exaggerated and spread worldwide.

The research team argued that NASA’s experiments assumed a sealed space smaller than 1㎥ and injected only one type of VOC, which does not apply to homes or offices. In reality, homes and offices are larger than 1㎥, not sealed, contain multiple types of VOCs mixed together, and these compounds are not injected at a constant rate as in the experiments.

Ultimately, the research team emphasizes that the air purification ability of plants has been overstated, and natural ventilation methods like opening windows are the most effective way to purify indoor air rather than relying on plants.

The lesson from this study is that over time, the experimental conditions NASA used have been overlooked, and only the results highlighting the effectiveness of plants in air purification have been emphasized, leading to an inflated perception of their effect.

Plants certainly have air-purifying functions. However, since their effect is not as significant as previously thought, shouldn’t we recognize that achieving noticeable results requires far more potted plants than expected?