Sarah, thank you for the thought-provoking post. Air exchange is the simplest way to rid our homes of toxic air, and you mentioned using air purifiers and opening windows. (The costs include buying a true HEPA filter and supplies and paying for extra electricity/fuel, but these are excellent methods.) However, I love that you suggested we consider something fun like using plants to detox the home.

Some of us tend to go overboard and buy multiple plants and all the accessories. Adding healthful foliage need not entail much extra cost or work. Here are some easy steps to take to introduce beneficial plants into the house:

• Ask a knowledgeable plant expert to suggest a nontoxic plant that is beneficial for freshening the air. (If you are lucky, your florist or nursery manager will be able to help. You could also seek a local university extension plant course instructor or resource center. Those of us living in college towns can often find botanists and other experts literally in our own backyards.)
• Start out small. (Buy one or two inexpensive plants till you know your needs and skills in the green-thumb category).
• Transfer plants to simple clay pots.( Forego the plastic and commercially painted ones. Some of the most beautiful pots I've seen were lovingly decorated by kids using recycled art supplies.)
• Consider a plant requiring minimal maintenance. You are busy enough, so try out one needing little feeding and attention. Even better, enlist your ego-oriented kids to care for it. (Just don't let them get too attached as did my son when trying to raise a redwood in our Midwestern home :-/).
• Sit back and enjoy. 

Again, Sarah, thanks for the suggestions on bringing more outside in! Next I hope to read about how to control plant pests with nontoxic, natural methods.