From some posted information by Collin Stoll:
The most natural and effective way of removing toxins from the air, is plants. Some especially effective houseplants are:
Studies done by Dr. William Wolverton at NASA and later on his own with the Plants for Clean Air Council) showed that these plants, the first three in paticular, not only removed, but metabolized formaldehyde, benzene, xylene, ammonia, and carbon monoxide.
They also balanced humidity levels and according to Dr. Wolverton, "excrete from their roots a complex nutrient solution of sugars and amino acids that allow them to cultivate certain microbes (which help break down toxins) while inhibiting others (molds etc.)."(New York Times,2/11/94?).
Needless to say house plants according to Chinese Medicine are excellent at absorbing dirty qi and giving off beneficial qi."