Changing the air filter for your furnace is an important step in good home maintenance. It does not matter if you own a home or live in a rental. Failing to install a clean furnace filter regularly can cost you. If the air filter is dirty, your furnace has to work much harder, which can cause it to fail. Since using a dirty air filter causes your furnace to exert more effort, your energy bill can increase greatly. You should install a new furnace filter every month during the cold weather seasons.
Switch off the main breaker that supplies power to your furnace. Make sure the thermostat is turned off as well in order to prevent dangerous sparks.
Find the location of the furnace filter. It will vary depending on what type of furnace you have. If the furnace has double stacking doors on the blower, remove both doors. The filter will likely be located on the bottom, but you will need to remove the top one first. In a downflow furnace, the filter might be in the upper compartment of the blower. If you have a horizontal furnace, check for a built-in rack that slides in and out.
Take the old, dirty air filter out of the furnace. Use the cloth to wipe away dust and grime.
Check the filter for an arrow along the edge of the cardboard frame. This will show you which direction to place the filter. The arrow will go the direction of the air flow. Install the air filter into the furnace the same way you removed the old one. The furnace may have a metal wire to hold the filter in place.
Close any doors to the furnace or vents. Turn the breaker on and then turn the thermostat back on.