I always have my ducts cleaned every few years before the winter. I did some research on the internet and called a number of companies before choosing Power Vac services. They have a very good reputation, have been around for over 40 years and belong to a national association of duct cleaners. They came on the scheduled day and did a complete system cleaning with their power vac truck. The vents were very dirty and they showed me what came out. They also did my dryer vent as a bonus. Although the price was not the cheapest I feel the quality of the service and their duct cleaning technology is more than worth it.