28 common ornamental plant species were tested for their ability to remove 5 volatile organic compounds (VOCs) from the air: benzene, toluene, octane, TCE, and terpene.

Plants were placed in airtight glass containers and exposed to ~10 ppm of gaseous pollutant. The containers were analyzed by gas chromatography-mass spectroscopy 3 and 6 hours after exposure to the test pollutants. Three replications of each species were tested with a fourth jar without the potted plant as a control measure. Leakage was also measured, and none was found during the testing.

The removal efficiency of different plant species varied between the pollutants:

• Benzene (0.03 to 5.54 µgm^–3 ·m^–2 ·h^–1 ), toluene (1.54 to 9.63), octane (0 to 5.58), TCE (1.48 to 11.08), a-pinene (2.33 to 12.21), and total VOC (5.55 to 44.04)

The plants were classified into superior, intermediate, and poor categories. Five species had the highest removal rates for all or most of the pollutants:

• For Hemigraphis alternata, Hedera helix, Hoya carnosa, Asparagus densiflorus, Tradescantia pallida the removal efficiency varied from 26.08 to 44.04 µgm^–3 ·m^–2 ·h^–1 of the total VOCs
• 6 plants had an intermediate phytoremediation potential ranging from 17.46 to 24.13  µgm^–3 ·m^–2 ·h^–1
• The rest with poorer efficiencies ranged from 5.55 to 12.98  µgm^–3 ·m^–2 ·h^–1

Researchers conclude, that: “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.”