Investigating the impact of plants on indoor air quality: a multi-scale cross-disciplinary approach

RHS project team
Dr Tijana Blanusa, Prof Alistair Griffiths
Curtis Gubb, University of Birmingham Dr Christian Pfrang, University of Birmingham
Start date
01/10/2016 00:00:00
End date
30/09/2020 21:00:00
The problem
Globally, indoor pollutants, such as carbon dioxide (CO2) and nitrogen dioxide (NO2), are reaching levels identified as dangerous by United States Environmental Protection Agency (EPA) and World Health Organization (WHO).

“Approximately 4.3 million people worldwide died prematurely due to indoor air pollution in 2012.”

High levels of CO2 have also been found to link to significant decreases in cognitive performance and decision making. Current means of managing indoor pollutant levels are costly and require energy consumption- plants could be a low-cost, easy-access, environmental solution to this problem.
Seven of the most popular indoor plant species (identified via plant sales in the RHS Wisley Garden Plant Shop) are being kept in chambers which simulate office environments. The plants are being exposed to different indoor air pollutants - identified in literature reviews as being the most common. 

The plants used in the research are:
  • Dracaena fragrans 'Lemon Lime',
  • Dracaena fragrans 'Golden Coast',
  • Guzmania ' Indian Night',
  • Hedera helix,
  • Spathiphyllum wallisii 'Bellini',
  • Spathiphyllum wallisii 'Verdi',
  • Zamioculcas zamiifolia.

Each plant has been chosen due to its popularity as an indoor house plant and for its structural composition, to ensure representation of a variety of leaf types, metabolisms and sizes.
Identify, if any of the trialled seven plant species can actively work to decrease levels of indoor air pollution – and of those than can decrease levels, establish whether the decrease is substantial enough to warrant recommendation as an effective means of indoor air pollution control.
Benefits to gardeners
We will provide recommendations on the most efficient plants to improve indoor air quality and human health and well-being
Summary of results
From the research so far plants have been found to reduce the concentration of harmful pollutants to a healthier concentration if, the environmental conditions are correct.

At typical ‘low’ indoor light levels removal rates of CO2 were generally low (< 3.9 mg hr-1). Differences between ‘dry’ and ’wet’ plants at typical indoor light levels were negligible in terms of room-level impact. Light compensation points (i.e. the light level where the CO2 assimilation equals zero) were in the typical indoor light range (1-50 µmol m-2 s-1) only for two studied Spathiphyllum wallisii cultivars and Hedera helix; these plants would thus provide the best CO2 removal indoors. Additionally, increasing indoor light levels to 300 µmol m-2 s-1 would, in most species, significantly increase their potential to assimilate CO2. Species which assimilated the most CO2 also contributed most to increasing RH.
Gubb, Curtis & Blanusa, Tijana & Griffiths, Alistair & Pfrang, Christian. (2018). Can houseplants improve indoor air quality by removing CO2 and increasing relative humidity? Air Quality, Atmosphere & Health. 10.1007/s11869-018-0618-9.

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