The short answer is every living plant purifies the air. All plants remove carbon dioxide from the air and use it in their metabolic processes. They also use oxygen, but actually produce more oxygen -- as a by-product of photosynthesis -- than they consume.
In a now-famous series of experiments, Dr. Bill Wolverton, a NASA scientist, showed the effectiveness of several species of commonly grown indoor (mostly tropical) plants in removing volatile organic compounds, VOC's, from the air.
Many people believe indoor plants are very effective at reducing illness cause by breathing VOC's in the home and office. The illness is often referred to as "Sick Building Syndrome." It is likely that many plants that are not used indoors are just as effective at removing VOC's and other air impurities from the air outdoors.
Here is a list of plants shown to be effective in removing VOC's from indoor air included in a very nice article on the subject.
More General Botany Questions
Century plant dying after bloom August 12, 2007 - My century plant is so tall that it is up to the top of the telephone pole top lines that carry our streets electric. I was wanting to know if you knew if I cut the stock off would it save the plant ... view the full question and answer
Native plants as accumulators of heavy metals in Texas March 29, 2008 - I would like to know of any native plants that could be used as hyperaccumulaters of heavy metals in Texas.
view the full question and answer
What does spp. stand for in Paspalum spp? From Arlington, TX. August 11, 2010 - What does the spp stand for when talking about Paspalum spp? view the full question and answer