Air duct cleaning on average takes anywhere from three to five hours, depending on the size of the system as well as the size of the home. The amount of registers you have and exactly how involved the actual cleaning is are additional factors.
In some instances it can actually take longer than five hours if the house is extremely large on one system. If you have a company that’s going to say that it’s going to take an hour to come out and clean there, they are more or less just going to come in, show you a shopvac and a feather duster, and do the same thing you could have actually done yourself.
You really just need to research a really good NADCA certified company, such as R.S. Andrews which is NADCA certified. This refers to the National Air Duct Cleaners Association. And really do your research and find a really good company, a good reputable company that’s going to come out and do a good and thorough job.