Why all indoor plants are equally as good at cleaning indoor air.

A lot of research has been carried out over the last twenty odd years into the ability of indoor plants to reduce the concentration of Volatile Organic Compounds in office air
Dr. Wolverton in the nineteen eighties carried out test chamber studies on some 50 different plant species (1), and since the year 2000 researchers at the University of Technology in Sydney have carried out more detailed studies on some 11 different indoor plants, both in test chambers and real office situations.(2) (3)

Over the last few years these studies have come to the notice of office and facility managers and architects, and have created quite a bit of interest, especially as VOCs create health problems in closed office environments. As a consequence of this interest we get asked quite often “which plant is the best at cleaning my office air?” In the past we have relied on the results obtained by Dr. Wolverton and published in his book “How to grow fresh air”. In his book Dr. Wolverton rates the VOC removal of individual indoor plants, using Formaldehyde as a reference VOC. The rating is out of 10, with the Sanseviera Trifisciata rating a lowly 2, and the Bamboo Palm rating 9 out of 10.

Based on more extensive testing at the University of Technology by Professor Margaret Burchett and her team of researchers we now feel that this is not very fair on the poor Mother in Law Tongue

Dr.Wolverton tested each plant in his test chambers over a relatively short period of time, and subsequent testing at the U.T.S. has shown that plants need a priming period of up to seven days before they reach their true VOC removal potential. By testing over a short period there are other factors which could influence the result and could account for the big differences in test results that Dr. Wolverton found. For instance some of the plants that showed high removal rates may already have been exposed to VOCs thus starting or being past their priming period, whereas the plants with low rating may not have had prior exposure to VOCs. By testing over a longer period this variable is removed.
Professor Burchett’s studies showed that after this priming period all the tested plants behaved in a similar manner, and were all able to reduce the VOC concentration in office air from quite high levels to levels below 100ppb.

Based on this research, when clients ask us which plant would better clean their office air, we can now say that all plants are good at it.

There is another reason why it does not make good sense to recommend particular plants at the expense of others for a particular office. Generally the indoor air has not been analyzed to see what particular VOC is dominant, and even if it has the number of predominant VOCs could be anywhere between 10 and 30, making the targeting of specific VOCs with specific indoor plants not practical. It is more practical to measure the total level of VOCs in the air (TVOC), and then reduce this. This is the approach taken by the Green Building Council of Australia (4), and the research by Professor Burchett has shown that for the indoor plants tested (5) , one plant is as good as another at accomplishing this.

1. “How to grow fresh air” by Dr. B.C. Wolverton and published by Penguin Books
2. “The potted plant microcosm substantially reduces indoor air VOC pollution: Office Field study” by Ronald Wood, Margaret Burchett et al. 2006
3. “The potted plant microcosm substantially reduces indoor air VOC pollution: Office Field study” by Ronald Wood, Margaret Burchett et al. 2006
4. “Technical Manual Green Star Office Design IEQ-13”
5. Plants tested are: Kentia Palm, Spathiphyllum Sensation and Spathiphyllum Petite, Dracaena Deremensis Janet Craig and Dracaena Marginata, Pothos, Schefflera Amata, Philodendron Congo, Sanseviera Trifisciata, Zanzibar Gem and Aglaonema.

Bio: Rudy Ursem is the General Manager / Owner of Green Design Indoor Plant Hire in Sydney Australia. He has operated this business for more then 25 years. Prior to that Rudy obtained a Civil Engineering degree at the University of NSW. Further information on the subject of this article can be obtained at http://www.greendesign.com.au