If it is approved term it will know what to keep

A surprising object called "Andrea", a kind of Bell plant green, is launched on the market this month. According to its designers, this system of air filtration by the leaves, the ground, roots and water, would be able to absorb ambient toxic gases. Another concept of filter plant (without Bell), called "Ecoplanter", is marketed for several years in the Japan. These products are adaptations of work initiated in the 1980s by the Nasa to purify the atmosphere of the spacecraft. They were conducted on indoor plants 50 and 100 volatile organic compounds (VOCs), large family of hydrocarbons, solvents, alcohols. Nevertheless, the solution was not accepted for spacecraft. Would be valid for our houses and apartments Plants well assimilated some gaseous pollutants, but their effectiveness is impossible to prove in the absence of rigorous scientific Protocol. Establish a Protocol, it is one of the objectives of the French research program Phyt's air on the purification of indoor air by plants, which combines the Faculty of pharmacy of Lille, a laboratory of the CNRS of Villeneuve - Ascq, the CSTB and the Association for the prevention of air pollution. "It is impossible to generalize, there is no ideal plant," insists Damien Cuny, Professor at the Faculty of pharmacy of Lille, which coordinates the program. Since 2001, Phyt's air studied three common pollutants (formaldehyde, benzene and carbon monoxide) and three plants: the spider, the pothos plant and the bamboo, placed in enclosures of 300 litres naturally lit and exposed for 24 hours. "Pollutant concentrations have decreased from 30 to 90, summarizes Damien Cuny. Nevertheless, each plant metabolizes or non-pollutant and specific manner. "Formaldehyde is not degraded benzene. Some plants do not withstand toxic residue, others defend themselves. As carbon monoxide, as the dose increases it becomes quickly toxic.

The importance of leaves

The assimilation of these substances through the leaves and soil. "For a passive system, the difference in biofiltration technologies that include a flow of air or water at the level of the substrate of the plant are leaves that metabolize pollutants", according to Damien Cuny. Depending on their size and their solubility, they penetrated by the stomata and cuticle on the surface of the leaves. They are then either processed dioxide of carbon and water, then rejected, to be included in other metabolisms. Pollutants in contact with the surface of the soil feeds the microfauna: bacteria, fungi and other microorganisms that live near the roots. Concepts where the air is ventilated, such as Andrea or Ecoplanter, are more complex but could be good for better efficiency.

The other point penalizing is that most of the research concern closed enclosures, with disparities of techniques and protocols that make comparisons difficult. The few studies carried out in premises of several cubic metres, are inconclusive and not easily exploitable. Hence the interest of the final stage of Phyt'air by 2011: move from the laboratory scale real premises, with well controlled, representative of actual exposures protocols. "We we put in the context of specific background pollution however Damien Cuny." If doses increase, is not the penalty count on plants to clean up! "He also said they have no effect on particles or other cigarette smoke. Also remains to ensure that they generate no allergens such as pollen or micro-organisms.

As many points to be validated by certified methods, like other techniques of purification of air in the market (photocatalysis, ionization...). By the end of the year, the Afnor should adopt a proposed at the initiative of the Ademe experimental standard to characterize them. If it is approved term, it will know what to keep. In the meantime, to reduce pollutants at source and ventilate enough parts remain the first evidence. Another certainty: the green plants make homes more pleasant!