Green plants are often presented as being able to purify indoor air. In many articles and advertisements, they are described as capable of absorbing pollutants present in our homes. This idea is partly based on old scientific work, but the reality is more nuanced when considering the conditions of an apartment or a house.
The origin of this belief dates back in particular to
experiments conducted in the late 1980s by NASA. These works showed that certain plants could absorb volatile organic compounds, such as benzene or formaldehyde, in closed experimental chambers. The researchers observed a measurable decrease in these substances in the presence of plants placed under controlled conditions.
The mechanism is indeed real. Plants can capture certain pollutants through their leaves and roots. Microorganisms present in the substrate also participate in the degradation of some molecules. This process relies on gas exchanges and the biological activity of the plant-soil system. On a theoretical level, the depolluting effect therefore exists.
However, laboratory conditions differ greatly from those of a typical home. The initial experiments were conducted in closed enclosures, with reduced air volumes and no renewal. In a real room, air circulates, windows open, and ventilation continuously renews the indoor air volume. This dilution significantly reduces the measurable impact of plants on pollutant concentrations.
Several recent studies have attempted to assess the real effectiveness of plants in domestic situations. The results indicate that, to achieve a significant reduction in pollutants in a standard room, a very high number of plants would be required. In theoretical estimates, it would be necessary to install several tens, or even hundreds of plants in a living room to obtain an effect comparable to that observed in the laboratory.
This does not mean that plants bring no benefit. They contribute to the relative humidity of the air through transpiration, which can improve comfort in some dry environments. Their presence also influences psychological well-being. Many researches show that a vegetated environment reduces perceived stress and improves the feeling of air quality, regardless of measured concentrations.
In practice, ventilation remains the most effective way to reduce indoor pollutants. Regular airing, maintenance of ventilation systems, and limiting sources of volatile compounds play a determining role. Plants can contribute to a more pleasant environment, but they do not replace active air renewal measures. Their depolluting role exists on a small scale, but it remains limited under the conditions of a common living room.