ANSWER

The Filter should be in one or two places, either the return grill which will be in a hallway near the thermostat. The return grill should have a small latch(es) or screws/nuts keeping it closed, the grill is hinged to allow it to swing open for easy filter changes. Simply remove old filter check the size thats written on it and replace with same size assuming it fit right. Replace it every 2 to 3 months depending how it looks. If your furnace is in the garage or a closet and you only have a flat return grill the filter will be in the bottom of the furnace, just open the bottom door and you will see it, pull it out and replace. Filters cost a few of bucks at Walmart, Loews or a DIY store.

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