With 20 plants, average levels of formaldehyde were only reduced from 856 ppb to 761 ppb. If potted plants do help treat sick building syndrome, Dingle concludes, the effect is psychological. They really make a place more comfortable and beautiful, but they do not clean the air of pollutants to any significant degree. Spider plants in the middle row blend into an indoor landscape. Jeff Llewellyn, an expert on indoor air quality with Britain's Building Research Establishment in Watford, says that the importance of such psychological factors shouldn't be underestimated.
Indoor plants are apparently useful in removing some pollutants.
B.C. Wolverton, Ph.D., a NASA researcher, presented a report in 1985 that found formaldehyde and carbon monoxide were removed by spider plants and golden pothos from closed chambers. Pollutant source removal or modification is an effective approach to resolving an indoor air quality problem when sources are known and control is possible. Routine maintenance of heating, ventilation and air conditioning systems such as periodic cleaning or replacement of filters is important. It is also important to allow time for building materials in new or remodeled areas to give off pollutants before the building is occupied. Increasing ventilation rates and air distribution often can be a cost effective means of reducing indoor pollutant levels.