Air pollution can rise indoors, resulting in a loss of concentration, falling productivity and a negative effect on the health of the occupants (sick building syndrome).


Plants have the potential to remove air pollutants. In the 1980s, NASA investigated the potential of 12 popular pot plants for improving indoor air quality. This showed that practically all the plants investigated were able to remove a large part of the contamination.


The most important mechanisms of air filtration through plants are: uptake of dissolved pollutants by the plant roots; direct absorption of volatile substances (VOC) through the stomata; dissolving volatile substances through the cuticle; enzymatic degradation within the plant. The plant architecture also has an influence on the uptake and degradation of these substances. Leaf structure and the density of stomata play an important role. The higher this density and the more relief on the blade, the higher the efficiency.


Indoors, light is also important: the more light, the higher the removal rate. The potting soil also has an important contribution, the plant is supported by the microbiological populations around the roots.


Concrete figures about how many plants are needed to have an effect on indoor air quality are much harder to find. Five to six pot plants, with sufficient leaf mass, for a surface area of 10 m² are recommended.

Urbanization in Flanders has increased sharply and most urban designs are relatively vegetation-free. Due to this increasing urbanization, the urban environment is also changing: the urban heat island effect, increasing air pollution and changed noise and light regimes.


Air pollution is a collective term for components in the air that have negative effects on human health and the ecosystem. The composition is different depending on the source; an urban environment will have a very different composition of air pollution than a more rural environment. Green in the city can offer a solution to reduce certain of these disadvantageous aspects.


Trapping of atmospheric aerosol particles by urban trees is determined by many parameters but also by leaf characteristics. For example, the presence of hairs, the type of wax layer and the salts and ions on the leaf surface influence the deposition rate. Moreover, the complexity of the leaf shape is important. For example, genera with complex leaves such as Pseudotsuga or Fraxinus are better able to capture fine dust than genera with simply formed leaves. The most effective ornamental shrubs for collecting fine dust are in decreasing importance: Buddleja davidii> Viburnum opulus> Carpinus betulus> Quercus ilex> Viburnum lantana> Rosa rugosa> Sorbus aria> Aesculus hippocastanum> Pseudotsuga menziesii> Acer campestre. The least effective species are Populus alba <Alnus glutinosa <Larix kaempferi <Larix decidua <Plantanus x acerilifolia <Acer pseudoplatanus <Robinia pseudoacacia <Quercus palustris <Rosa canina <Liquidambar styraciflua.

In this project, data are collected concerning extra functions that can be attributed to plants such as air purifying, therapeutic and climate-regulating effects. Via interactive sessions, a study day and a practice oriented brochure, these data are transferred to the ornamental sector (producers and other stakeholders). This will allow the Flemish ornamental grower to tailor his crops to a current social need, namely beneficial effects on the indoor and outdoor climate by plants. Thanks to this knowledge, the ornamental sector can place itself on the market not only as a producer of plants, but also providing ecosystem services by increasing the use of ornamental plants (both locally and internationally). The outcome of this project might lead to further diversification and production of specific ornamentals for both indoors and outdoors.


The landscaping sector also benefits directly from the project results. They are the requesting party to know which plants should be planted with respect to remove air pollutants in an urban environment. Green suppliers for buildings and constructors of vertical greenery or green roofs also receive objective information about the air-purifying effect of ornamental outdoor plants. In addition, local strategies for urban green-space planning incorporating ecosystem services of plants can use the scientific knowledge obtained in this study.