An a green wall with dense foliage could reduce some air pollutants. However, their effects depend of level to assessment or scale. Generally, these structures produce effects on microclimate conditions, and also ameliorate the air quality on local scale. Therefore, the air pollution filtering of green walls, could have important effects on the local scale, but this function, probably depends of density of foliage, plant's species, the leaf area, and another factors related. Thus, I think the pollutants filter capacity of green walls could be a environmental important mitigating effect, while green walls augment their area on the urban areas.