Screening Indoor Plants for VOC Removal Efficiency

Twenty-eight ornamental species commonly used for interior plantscapes were screened for their ability to remove five volatile indoor pollutants: aromatic hydro- carbons (benzene and toluene), aliphatic hydrocarbon (octane), halogenated hydrocar- bon [trichloroethylene (TCE)], and terpene (a-pinene). Individual plants were placed in 10.5-L gas-tight glass jars and exposed to ’10 ppm (31.9, 53.7, 37.7, 46.7, and 55.7 mgm–3) of benzene, TCE, toluene, octane, and a-pinene, respectively. Air samples (1.0 mL) within the glass containers were analyzed by gas chromatography–mass spectroscopy 3 and 6 h after exposure to the test pollutants to determine removal efficiency by monitoring the decline in concentration over 6 h within sealed glass containers. To determine removal by the plant, removal by other means (glass, plant pot, media) was subtracted. The removal efficiency, expressed on a leaf area basis for each volatile organic compound (VOC), varied with plant species. Of the 28 species tested, Hemigraphis alternata, Hedera helix, Hoya carnosa, and Asparagus densiflorus had the highest removal efficiencies for all pollutants; Tradescantia pallida displayed superior removal efficiency for four of the five VOCs (i.e., benzene, toluene, TCE, and a-pinene). The five species ranged in their removal efficiency from 26.08 to 44.04 mgm–3m–2h–1 of the total VOCs. Fittonia argyroneura effectively removed benzene, toluene, and TCE. Ficus benjamina effectively removed octane and a-pinene, whereas Polyscias fruticosa effectively removed octane. The variation in removal efficiency among species indicates that for maximum improvement of indoor air quality, multiple species are needed. The number and type of plants should be tailored to the type of VOCs present and their rates of emanation at each specific indoor location.