Use a company that will provide a fair quote, based on the service that they will provide. Be weary of companies that advertise one price for a whole house. Think about it, would a painter paint any size house for one low price? Neither can an air duct cleaner PROPERLY clean the WHOLE house, no matter how many systems or air vents are in the home for one low price.
"This a very professional company that came the next day after being contacted late in the day prior. The two guys that came to the door that did the work were well dressed and very courteous. They cleaned my diver vent and it works perfectly. I have their literature and will be calling them when I m ready for duct cleaning. Nice equipment too! Thanks for the good work. Nice not to have scroungy guys showing up at the door. "