Thanks to everyone who responded with recommendations for residential air duct cleaners! Here are the tips I received: We used Air Duct Maintenance - (800) 922-DUCT. They did a great job and came extremely well recommended. ** Servicemaster of Greater Pgh. I used to work there and they do a great job. 412 826-1010 tell them Debi from HP told you to call. They do a much more thorough job than some of theses places that just vaccum the duct openings. They send a device all throughout the duct cleaning it out. ** http://blogs.consumerreports.org/home/duct_cleaning/ ** I haven't used one but just wanted to pass along that there are filters you can put on the inside of the vents. You can get them at Home Depot, or a sheet of the material that you cut up yourself. All best, Ariana