Can houseplants improve indoor air quality by removing CO2 and increasing relative humidity?
High indoor CO2 concentrations and low relative humidity (RH) create an array of well-documented human health issues. Therefore, assessing houseplants’ potential as a low-cost approach to CO2 removal and increasing RH is important. We investigated how environmental factors such as ‘dry’ (< 0.20 m3 of water per m3 of substrate, m3 m−3) or ‘wet’ (> 0.30 m3 m−3) growing substrates, and indoor light levels (‘low’ 10 μmol m−2 s−1, ‘high’ 50 μmol m−2 s−1, and ‘very high’ 300 μmol m−2 s−1) influence the plants’ net CO2 assimilation (‘A’) and water vapour loss. Seven common houseplant taxa—representing a variety of leaf types and sizes—were studied for their ability to assimilate CO2 across a range of indoor light levels. Additionally, to assess the plants’ potential contribution to RH increase, the plants’ evapo-transpiration (ET) was measured. At typical ‘low’ indoor light levels, ‘A’ rates were generally low (< 3.9 mg h−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.
KeywordsDracaena Drought Hedera Indoor light Indoor air quality Spathiphyllum
Relative humidity (%)
Daily light integral (mol m−2 d−1)
Substrate moisture content (m3 m−3)
Light compensation point (μmol m−2 s−1)
Uptake or emission of CO2 by potted-plant microcosm
Leaf area (m2)
Evapo-transpiration per unit leaf area (g cm−2)
This work was supported by the Royal Horticultural Society and the Engineering and Physical Sciences Research Council (EPSRC). The authors would also like to thank Dr. Dalila Touhami, Dr. Fiona Lahive, Dr. Sarah Kemp, Rob Stirling, Val Jasper, Matthew Richardson, and Will Johnson for their practical guidance and support.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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