Have you seen the TV commercial where the guy demonstrates an air filter that you can buy for your home or office? He talks about all of the problems with air that can be found in homes and how this filter can eliminate most of those pollutants. All you have to do is plug it into the wall, turn it on and enjoy clean filtered air. Of course there are a few maintenance activities you have to be aware of.

I got to thinking about the commercial the other day, and realized that most gardeners already have air purifiers in their homes if they are caring for houseplants. Several years ago, NASA conducted a study to determine if houseplants could act as air filters inside space stations in order to purify the air inside these living spaces.

The results indicated that houseplants were terrific air purifiers.

What's neat about houseplants is that they don't make noise when they operate. They don't need to be plugged into a wall, so no money is spent on electricity. In addition, they get bigger each year, so they actually improve their ability to clean the air in your home or office.

Just like the purchased machine, there is some minimal maintenance associated with growing houseplants. You have to water as needed, fertilize about once a month, perhaps repot once every two or three years, and clean the leaves every six months.

If you think you would like to purify the air in your home or office, go to your local garden center and ask the clerk to show you one of the following: ficus, pothos, ivy, dracaena, mother-in-law's tongue or peace lily. Many other plants make good air filters, but these are some of the more common ones.

To do an adequate job of filtering the air in your home or office, purchase one 6- to 8-inch (size refers to the pot size) plant for every 90 square feet of floor space if your average ceiling height is 8 to 9 feet. I would probably get more than this to improve filtering.

So why do you need an air filter in your home or office? During the 1970s architects and builders began abandoning natural building materials for synthetic ones. These synthetic materials often release toxins -- such as benzene, formaldehyde, carbon monoxide and carbon dioxide -- in low concentrations into the atmosphere. This release, combined with the lack of air circulation due to enhanced use of air conditioning, may increase the concentrations of toxins into the enclosed atmosphere.

Houseplants also provide the homeowner with other benefits. Plants are aesthetically pleasing and add to the beauty of your home. Most interior decorators add houseplants to their designs for this reason.

Since the early 1970s, the field of therapeutic horticulture has mushroomed. Psychologists and physical therapists recognized that patients who cared for plants rehabilitated sooner or maintained a better disposition for longer periods of time.

If you want to clean up the air in your home or office and enjoy some relaxation time, purchase a houseplant or two, take them home and care for them. You will enjoy the results of better health through a cleaner, green environment.

Send your gardening and landscape questions to Paul Schnare at P.O. Box 699, Cape Girardeau, Mo. 63702-0699 or by e-mail to news@semissourian.com.