As a homeowner you should always make sure the filter is regularly changed. When you purchase a filter, the manufacturer’s instructions include a recommendation for how often it should be changed. Filters can become clogged much sooner than that recommendation depending on factors in the home, such as excessive dust, pet hair, or cigarette smoke. Keep an eye on the filter and change it when it appears to be clogged or dirty, even if it’s before the recommended date. And remember to always aim the arrow on your filter at the furnace.