What Do Dyson Vacuum Filters Do? By definition, a filter removes substances from air or water. In your home, your HVAC system has an air filter, your dishwasher (and possibly also your sink) has a water filter and your water dispenser in your refrigerator has a filter. All these filters do their job of filtering out impurities in the air and water. But eventually, they become full and unable to filter anything else. ..