Talk about a quick fix: Adding plant life to a home has been proven to remove toxins from indoor air. Keeping a home healthy has never been so low-maintenance. Bill Wolverton is an authority on plants as purifiers, and his book How to Grow Fresh Air is an excellent primer on using plants to improve your indoor air quality.

The job can be a big one. Indoor air can be more seriously polluted than outdoor air-even in the largest and most industrialized cities, according to the Environmental Protection Agency (EPA). If you're not running a coal-fed power plant in your bedroom, this might seem hard to believe. But there are myriad sneaky sources of indoor air pollution, such as carpeting, furniture made of pressed-wood products, asbestos-containing insulation, and cleaners made with harsh chemicals. Ironically, doing a good job of insulating and sealing your home (a good thing) can compound the problem (a bad one) if it's not properly ventilated.

Wolverton first discovered the little green guys' powers while researching the possibility of moon bases for NASA. The 1973 Skylab mission led to a breakthrough. "We found over 300 VOCs [volatile organic compounds] in the air inside the spacecraft," Wolverton recalls. "Then, just out of curiosity, we started looking at low-light-requiring plants, like houseplants. What if you put them in a chamber and injected these nasty chemicals into it? Lo and behold, we found these common houseplants could literally remove the chemicals." He says it's a defense mechanism that has an obvious explanation: Most evolved underneath the canopy of the tropical rain forest, where the moist conditions encourage the growth of mold and mildew, which are threats to the plants.

Other researchers have made similar findings. Margaret Burchett and Ron Wood (no, not that one) at the University of Technology in Sydney, Australia, pumped chemicals into airtight glass containers, only one of which held plants. At the end of the experiment, the receptacle with plants contained much less toxic air than the one without. Virginia Lohr and Caroline Pearson-Mims of Washington State University discovered less dust accumulation in rooms with plants present. Their research has also shown that plants reduce stress and increase worker productivity. (If formaldehyde reduction doesn't seduce you into buying a few leafy green friends, perhaps the prospect of lowered anxiety will.)

Here, Wolverton offers up some tidbits to help you understand the science behind plant power, and some tips on getting the most out of your natural air purifiers.

Microbes. Wolverton says he discovered that certain plants, such as the peace lily and English ivy, are far superior at removing chemicals from the air, and he determined that this is partially due to unique microbes on and around the plant roots. The root microbes (microorganisms living on the plant that are invisible to the naked eye) break down the pollutants and turn them into food for the plant.

Transpiration. Wolverton found the most effective plants had a high transpiration rate, which means they emit moisture at a faster rate. As the plants give off moisture, they suck water up from the roots, establishing a small convection current that pulls polluted air down from the surrounding environment and into the roots.

Hydroculture. To maximize your plant's transpiration rate without increasing the possibility of mold growth, Wolverton suggests growing your houseplants this way: Place clay pebbles-instead of potting soil-in a pot with no holes. Insert a small length of pipe into the pot; this is how you'll water the plants, using it like a small funnel. Maintain a constant level of about two inches of water (water-loving plants might like three inches, he says). You can drop a dipstick into the pipe to check the level. He suggests occasionally adding some Miracle-Gro or other fertilizer to the pot. Wolverton says this improves the plants' air-purifying capability by 100 to 200 percent.

Room size. Wolverton recommends two to three mature plants per 100 square feet to improve indoor air quality. If you have a serious indoor air quality problem, you'll need a large number of plants. But if you're just starting out, remember: One plant is better than no plants.

Light and temperature. All plants need some light, so consider whether you call home a spacious window-filled house in Florida or a cave-like Manhattan studio. Wolverton notes that most plants thrive in temperatures we are comfortable in, but that some have particular light and temperature needs. To a certain degree, you can control your climate. Wolverton, for instance, lives in a humid climate, but his air-conditioning helps control indoor moisture levels.

Go with what you like In his book, Wolverton lists the 50 plants that best purify air, beginning with the most effective, the Areca palm. Considering the variety out there, he says, buy what suits your style. Wolverton's favorite is the lady palm, which requires a good amount of light (categorized as "semi-sun" in the book). If you don't have enough light, he suggests something such as the snake plant, also called the "mother-in-law's tongue." It will grow with very little light and very little water, making it, appropriately, difficult to get rid of.

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