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Plants Clean Air and Water for Indoor Environments

Plants can filter indoor air pollutants and also water -- according to research by NASA scientists. Your office and home might benefit from these houseplants with high performance air filtration capabilities.

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It's time to think about indoor air quality again...and make sure your office, home and community access rooms are "greenified" with natural air filters -- plants.

Why now? Whether it's the change of seasons, or after a long vacation, or a new space, plants can become ragged with neglect, live out their lifespan, or just need a gardener's loving touch. With purpose! In this case, for indoor air quality improvement.

First, a little about the fascinating and enlightening history of NASA's breakthrough research for those of us earthbound...

Bill Wolverton's Plant Research for Indoor De-pollution

In the late 1960s, B.C. “Bill” Wolverton was an environmental scientist working with the U.S. military to clean up the environmental messes left by biological warfare centers. At a test center in Florida, he was heading a facility that discovered that swamp plants were actually eliminating Agent Orange, which had entered the local waters through government testing near Eglin Air Force Base.

The Stennis’ Environmental Assurance Program

The goals of the air quality program were to clean the Center of chemicals left behind through wastes and to supply information to NASA engineers about closed-environment "eco" support that may prove helpful in designing sustainable living environments for long-term habitation of space. A tertiary goal was to provide usable technologies to NASA’s Technology Utilization Program, essentially making the research available to the American public.

Living Environments Remediation

The first step for Wolverton’s research was to continue the remediation work he had started with the military. He was tasked with using plants to clean waste water at the NASA Center. To this day, Wolverton’s design, which replaces a traditional septic system with water hyacinths, is still in use. His research then turned to using plants to improve air quality.

VOCs in the Air from Offgasing

In 1973, NASA scientists identified 107 volatile organic compounds (VOCs) in the air inside the Skylab space station. Synthetic materials, like those used to construct Skylab, give off low levels of chemicals. This effect, known as off-gassing, spreads the VOCs, such as formaldehyde, benzene, and trichloroethylene, all known irritants and potential carcinogens. When these chemicals are trapped without circulation, as was the case with the Skylab, the inhabitants may become ill, as the air they breathe is not given the natural scrubbing by Earth’s complex ecosystem.

Energy Efficiency = Airtight Buildings = Sick Buildings

Around the same time that Wolverton was conducting his research into VOCs, the United States found itself in an energy crisis. In response, builders began making houses and offices more energy efficient. One of the best ways to do this was to make the buildings as airtight as possible. While keeping temperature-controlled air in place, this approach reduced circulation. Combined with the modern use of synthetic materials, this contributed to what became known as Sick Building Syndrome, where toxins found in synthetic materials become concentrated inside sealed buildings, making people feel sick.

Restore Personal Environments with Plants -- Nature's Life Support System

The solution Wolverton sought was not to make indoor environments less energy efficient or to move away from the convenience of synthetic materials; rather, the plan was to find a solution that restores personal environments. The answer, according to a NASA report later published by Wolverton in 1989, is that "If man is to move into closed environments, on Earth or in space, he must take along nature’s life support system." Plants.

BioHome for Plants ... + a Few People

One of the NASA experiments testing this solution was the BioHome, an early experiment in what the Agency called "closed ecological life support systems."

The BioHome was a tightly sealed building constructed entirely of synthetic materials, and was designed as suitable for one person to live in, with a great deal of the interior occupied by houseplants. Before the houseplants were added, though, anyone entering the newly constructed facility would experience burning eyes and respiratory difficulties, two of the most common symptoms of Sick Building Syndrome.

Once the plants were introduced to the environment, analysis of the air quality indicated that most of the VOCs had been removed, and the symptoms disappeared.

Wolverton's Move to Bioremediation Research

After serving over 30 years as a government scientist, Wolverton retired from civil service but continued his work in air and water quality by founding Wolverton Environmental Services Inc. The company, based just down the road from Stennis in Picayune, Mississippi, is an environmental consulting firm that gives customers access to Wolverton’s decades of cutting-edge bioremediation research.

How to Grow Fresh Air

Wolverton published his findings about using plants to improve indoor air quality in dozens of technical papers while with the Space Agency and as a simple consumer-friendly book, How to Grow Fresh Air: 50 Houseplants That Purify Your Home or Office. In it, he explains, in easy-to-understand terms, how plants emit water vapor that creates a pumping action to pull contaminated air down around a plant’s roots, where it is then converted into food for the plant. He then goes on to explain which plants and varieties remove the most toxins, as well as to rate each plant for the level of maintenance it requires. The book has now been translated into 12 languages and has been on the shelves of bookstores for nearly 10 years.

Growing Clean Water

Wolverton has also published a companion book, Growing Clean Water: Nature’s Solution to Water Pollution, which explains how plants can clean waste water.

Sustainable Indoor Ecosystems

Wolverton Environmental Services Inc. designed a sustainable ecosystem to show how a building’s circulation system and a rooftop garden could work in tandem to clean indoor air.

Another one of Wolverton’s discoveries is that the more air that is allowed to circulate through the roots of the plants, the more effective they are at cleaning polluted air. To take advantage of this science, Wolverton has teamed with the Japanese company, Actree Corporation, to develop what the Japanese firm is marketing as the EcoPlanter.

Using high-efficiency carbon filters and a root-level circulation system, the EcoPlanter pot allows the plant to remove approximately 200 times more VOCs than a single traditionally-potted plant can remove.

The company has recently begun to assess the ability of the EcoPlanter to remove formaldehyde from the many travel trailers furnished by the Federal Emergency Management Agency to victims of Hurricane Katrina. The interiors of the trailers make heavy use of particleboard, which off-gasses formaldehyde. Many of the trailers have been found to exceed the recommended levels of formaldehyde for human safety. Initial tests of the EcoPlanter have been very encouraging, but other testing is still needed.

Psychological Role of Plants

Research has also suggested that plants play a psychological role in welfare, and that people actually recover from illness faster in the presence of plants. Wolverton’s company is working with another Japanese company, Takenaka Garden Afforestation Inc., of Tokyo, to design ecology gardens. These are carefully designed gardens that help remove the toxins from the air in hospitals, as well as provide the healing presence of the foliage.

HVAC Plant-based Filtration Systems

In a partnership with Syracuse University, Wolverton Environmental is engineering systems consisting of modular wicking filters tied into duct work and water supplies, essentially tying plant-based filters into heating, ventilation, and air conditioning (HVAC) systems.

Whole-building Forced Air Eco-Quality System

This whole-building approach has recently been licensed by Wolverton to Phytofilter Technologies Inc., of Saratoga Springs, New York, which is currently constructing a prototype of a system that is intended to clean the water and air circulation systems of entire buildings using the natural abilities of plants.

The design includes units that are built into existing HVAC units. The plants can be placed throughout buildings, in atriums, or in roof gardens and then hooked into the building’s HVAC units through forced-air filters.

List of High-Performance Air Filtering Plants

This list of air filtering plants was compiled by NASA as part of the NASA Clean Air Study, which researched ways to clean air in space stations.

Plants absorb carbon dioxide and release oxygen, as all plants do, and these plants also eliminate significant amounts of benzene, formaldehyde and/or trichloroethylene from the air, helping neutralize the effects of sick building syndrome.

Certain common indoor plants may provide a natural way of removing toxic agents and provide beauty and restful aesthetics for stress reduction at the same time.

  • English Ivy (Hedera helix)
  • Spider plant (Chlorophytum comosum)
  • Golden pothos or Devil's ivy (Scindapsus aures or Epipremnum aureum)
  • Peace lily (Spathiphyllum 'Mauna Loa')
  • Chinese evergreen (Aglaonema modestum)
  • Bamboo palm or reed palm (Chamaedorea sefritzii)
  • Snake plant or mother-in-law's tongue (Sansevieria trifasciata 'Laurentii')
  • Heartleaf philodendron (Philodendron oxycardium, syn. Philodendron cordatum)
  • Selloum philodendron (Philodendron bipinnatifidum, syn. Philodendron selloum)
  • Elephant ear philodendron (Philodendron domesticum)
  • Red-edged dracaena (Dracaena marginata)
  • Cornstalk dracaena (Dracaena fragans 'Massangeana')
  • Janet Craig dracaena (Dracaena deremensis 'Janet Craig')
  • Warneck dracaena (Dracaena deremensis 'Warneckii')
  • Weeping Fig (Ficus benjamina)
  • Gerbera Daisy or Barberton daisy (Gerbera jamesonii)
  • Pot Mum or Florist's Chrysanthemum (Chrysantheium morifolium)
  • Rubber Plant (Ficus elastica)

Most of the plants on this list evolved in tropical or subtropical environments. Due to their ability to flourish on reduced sunlight, their leaf composition allows them to photosynthesize well in household light.

NASA recommends adopting 15 to 18 good-sized houseplants in six- to eight-inch diameter containers in a 1,800 square-foot house. The amount of exposed surface soil is also important, as microorganisms in the soil consume trace amounts of airborne toxins as well.

NASA Research information.

Wolverton Environmental:

Edited by Carolyn Allen
| air quality |


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