In the late 1980s, a study by NASA and the Associated Landscape Contractors of America (ALCA) was conducted to find ways to purify the air for extended stays in orbiting space stations. The study resulted in excellent news for homeowners and office workers everywhere, because it concluded that common houseplants not only make indoor spaces more attractive, they also help to purify the air!

While it's a well known fact that plants convert carbon dioxide into oxygen through photosynthesis, the NASA/ALCA study showed that many houseplants also remove harmful elements such as trichloroethylene, benzene, and formaldehyde from the air.

The advantage that houseplants have over other plants is that they are adapted to tropical areas where they grow beneath dense tropical canopies and must survive in areas of low light. These plants are thus ultra-efficient at capturing light, which also means that they must be very efficient in processing the gasses necessary for photosynthesis. Because of this fact, they have greater potential to absorb other gases, including potentially harmful ones.

In the study, NASA and ALCA tested primarily for three chemicals: formaldehyde, benzene, and trichloroethylene. Formaldehyde is used in many building materials including particle board and foam insulations. Additionally, many cleaning products contain this chemical. Benzene is a common solvent found in oils and paints. Trichloroethylene is used in paints, adhesives, inks, and varnishes.


Golden Pothos
NASA noted that some plants are better than others in treating certain chemicals. For example, English ivy, gerbera daisies, pot mums, peace lily, bamboo palm, and Mother-in-law's Tongue were found to be the best plants for treating air contaminated with benzene. The peace lily, gerbera daisy, and bamboo palm were very effective in treating trichloroethylene. Additionally, NASA found that the bamboo palm, Mother-in-law's tongue, dracaena warneckei, peace lily, dracaena marginata, golden pathos, and green spider plant worked well for filtering formaldehyde. After conducting the study, NASA and ALCA came up with a list of the most effective plants for treating indoor air pollution.

The recommended plants are listed below. Note that all the plants in the list are easily available from your local nursery.

'Oxycardium', heartleaf philodendron, Philodendron scandens

Elephant ear philodendron, Philodendron domesticum

'Massangeana', cornstalk dracaena, Dracaena fragrans

English ivy, Hedera helix

Spider plant, Chlorophytum comosum

'Janet Craig', Janet Craig dracaena, Dracaena deremensis

'Warneckii', Warneck dracaena, Dracaena deremensis

Weeping fig, Ficus benjamina

Golden pothos, Epipiremnum aureum

'Mauna Loa', peace lily, Spathiphyllum

Selloum philodendron, Philodendron selloum

Chinese evergreen, Aglaonema modestum

Bamboo or reed palm, Chamaedorea sefritzii

Snake plant, Sansevieria trifasciata

Red-edged dracaena, Dracaena marginata

For an average home of under 2,000 square feet, the study recommends using at least fifteen samples of a good variety of these common houseplants to help improve air quality. They also recommend that the plants be grown in six inch containers or larger. 

Reprinted from Do It Green! Minnesota,