I was thinking about getting my air ducts in my home cleaned. I found a pretty good information page which you can read

http://www.air-techinternational.com/homeprep.html

I think it is a good idea but I did not realize it would probably cost 500 dollars or so. Also it is kind of scary thinking how much damage a bad person could do. I guess they need to be licensed and such. I guess I am lazy also because I dont want them taking off all the painted air vents I currently have.