Poor quality indoor air, the E-P-A reports, can increase the risk of asthma, respiratory problems, cancer and heart disease—but you don’t have to put up with it. Here’s how to improve your indoor air: Change air filters monthly. They trap pollutants. Dust and vacuum regularly. Have your air ducts professionally cleaned. Contaminants get pulled into the H-V-A-C system, make it work harder, and increase your electric bill. To find a National Air Duct Cleaning Association-certified professional, visit Breathing-Clean--dot--com.