Swindlers can scam homeowners with phony air-duct cleaning schemes—but you can protect yourself. It helps to beware of “blow-and-go” scams. Companies offer bargain-basement prices, then do an inferior job, leaving dirt and contaminants inside the system that then circulate throughout the ductwork and get into the air you breathe. Fortunately, there are qualified air duct cleaners. National Air Duct Cleaners Association members have technicians with advanced training and certifications. To find one, search the online directory at n-a-d-c-a--dot--com.