In 2006, the Sierra Club contacted Dr. Wolverton to install his portable high efficiency plant purifier into a FEMA trailer that tested high for formaldehyde.  Within a few days the plant air purifier reduced the level of formaldehyde inside from 0.18 parts per million to 0.03 parts per million in the trailer - taking the toxin level from unsafe to within legal limits of 0.05 ppm determined by the World Health Organization.The previous work that led to the FEMA trailer demonstration began with NASA research into “closed ecological life support systems”.  In 1984, NASA first published studies demonstrating that interior plants could remove VOCs from sealed test chambers.  With the BioHome project, NASA ramped up their study of the cleansing powers of nature through the synergistic reactions taking place between plants and their root  microbes.  The BioHome was a very tightly constructed dwelling equipped to provide a fully functional habitat suitable for one person.  “The Biohome was equipped with monitoring ports in each outside door for sampling air from inside this tightly sealed structure.  

Before plants were added, mass spectrometer/gas chromatograph (mass spec/GC) analyses of the indoor air showed high levels of VOCs off-gassing from interior synthetic materials.  Upon entering the building, one experienced severe burning of the eyes and respiratory discomfort, both classic symptoms of ”sick building syndrome.”Interior foliage plants were placed throughout the living quarters to evaluate their ability to remove VOCs out-gassed from the newly constructed and furnished facility. A small prototype fan-assisted plant filter was also placed in the living quarters.  This plant filter had the VOC removal capacity of 15 standard potted plants. Air quality was again tested using mass spec/GC analyses.  Results showed that most ot the VOCs had been removed.  The ultimate test was the fact that one no longer experienced the symptoms of “sick building  syndrome”.  This was the first “real world” application using interior plants to alleviate indoor air pollution”.

Other NASA research undertaken by Dr. Wolverton included the monitoring of rate of reduction of measured levels of various gaseous pollutants of known quantity introduced into sealed “table-top” test chambers which had various “house” plants growing inside.  manual for hunter air purifierThe plants always reduced the levels of pollutants, without exception.top rated ozone free air purifiersOn average, Americans spend 90 percent of their time indoors. crystal air purifierUnfortunately, indoor air in today's homes, businesses, and schools is often more polluted than outdoor air. In fact, the Commonwealth Scientific and Industrial Research Organisation estimates that occupants of new homes may be exposed to many times the maximum allowable limits of indoor air pollutants such as formaldehyde and benzene.

Exposure to formaldehyde irritates the eyes, nose and throat, can cause headaches and allergic contact dermatitis, and has been linked to asthma. Benzene irritates the eyes and skin. Indoor air pollution is caused mainly by synthetic building materials, finishes and furnishings that off-gas pollutants. It is also caused by the use of personal-care products, pesticides and household cleaners and by biological sources such as insects, pests, molds and other fungi. Both builders and homeowners can improve indoor air quality (IAQ). Builders can help by using green building materials instead of materials that contain volatile organic compounds, as many traditionally manufactured carpeting, cabinets, drywalls and paints do. Builders also can design adequate ventilation systems that effectively remove toxins and replace them with fresher air. Homeowners can contribute to improving IAQ by reducing the amount of synthetics and known pollutants they use at home and by opening windows and doors for fresh air as seasonally appropriate.

Another important way homeowners can improve IAQ is to add live indoor plants. Certain indoor plants have been proven to help absorb harmful toxins in the air, such as formaldehyde, benzene, trichloroethylene and carbon monoxide. The National Aeronautics and Space Administration (NASA) and the Associated Landscape Contractors of America (ALCA) conducted research using popular varieties of ornamental plants to determine their effectiveness in removing several key pollutants associated with indoor air pollution. Their findings include the following: Indoor plants are capable of removing low levels of pollution from the air through the tiny openings in their leaves.Plant roots, assisted by an activated carbon filter and a fan, can remove air pollutants at higher concentrations. The filters around the plant roots remove and biologically degrade pollutants before they accumulate. This is an advantage over advanced-technology carbon filters, which remove pollutants from the air but then require careful disposal.

Under some conditions, live plants can effectively remove benzene, formaldehyde, carbon monoxide and nitrogen oxides (undesirable products of burning tobacco and wood) from the air.Philodendrons, spider plants and golden pothos are the most effective at removing formaldehyde molecules.Flowering plants such as gerbera daisies and chrysanthemums are most effective at removing benzene.Spider plants placed in closed chambers with 120 parts per million (ppm) of carbon monoxide remove 96 percent of the contaminant in 24 hours. Similarly, spider plants placed in closed chambers with 50 ppm of nitrogen oxide remove 99 percent of it from the air in 24 hours. According to the NASA/ALCA research, the 10 plants most effective in removing formaldehyde, benzene, trichloroethylene and carbon monoxide from the air are: Bamboo palm (Chamaedorea seifrizii)Chinese evergreen (Aglaonema modestum)English ivy (Hedera helix)Gerbera daisy (Gerbera jamesonii)Janet Craig (Dracaena fragrans "Janet Craig")Marginata (Dracaena marginata)Mass cane/corn plant (Dracaena fragrans "Massangeana")Mother-in-law's tongue (Sansevieria trifasciata laurentii)Pot mum (Chrysanthemum morifolium)Peace lily (Spathiphyllum "Mauna Loa")