You could be more comfortable at home for less money. The Environmental Protection Agency says cleaning a heating and cooling system lets it run more efficiently so it’s less likely to break down, lasts longer and operates more effectively. So, how to choose a cleaning contractor? Look for a National Air Duct Cleaners Association member. These contractors sign a Code of Ethics, meet strict requirements and have a certified Air Systems Cleaning Specialist on staff. You can find these professionals at n-a-d-c-a--dot--com.