Living in Arizona there is a lot of dust-inside of my house has become very dusty, and since I keep the windows/doors closed because of allergies I was very perplexed. After dusting twice a day for several months I finally Called Honest Air and day before yesterday Ken came out-we have a flat foam roof with unit on top--he re-taped all the areas even tho the caulking looked good and he couldn't find any holes-48 hours later and there is still no dust on my furniture--moral to story-if you have a flat roof and lots of dust in your home have the connections from a/c to roof checked out; and re-caulked/retaped if necessary.
Honest Air installed our Trane five years ago and they have been a great company to deal with ever since.