Homeowners should change a furnace filter at least every three months, and check it every month to see how much dust has accumulated on the filter. Individuals can change a furnace filter when the medium gets dirty.
Change a basic fiberglass or paper disposable filter every one to two months. An electrostatic or HEPA filter gets changed every two to four months. Things such as furry pets, smokers and a constantly running heating fan may cause dust to accumulate faster on the filter. Reusable electrostatic filters trap smoke and smaller particles, and these filters must be cleaned and rinsed with a garden hose. Some furnace filters can trap micro-organisms.