Everything I've read says it's bunk.
The best things you can do to improve indoor air quality, according to what I've read, is to install a Progressive Media Whole House air cleaning filter. You change the filter about 1x a year, it costs about 500 (about the same as 1 duct cleaning session), and it seems to really work, from what I've read on the hvac boards.
The website for it is
www.ultravation.com I'm getting one put in when they swap out the a/c. The filters are about 45 bucks.
The other best thing you can do is get rid of all your carpets. THink of them as sweaters you walk on that you can never really clean. THey harbor literally millions of dust mites that feed on shed skin cells, dirt, and food. THeir feces can cause asthma and breathing problems. The chemicals used to clean the carpets can cause autoimmune issues in people who are prone to it.
Just my gross-out 2c for the day

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