Furnace filters should be changed regularly to maintain efficient heating and clean indoor air. Furnace filters are easily changed by sliding out the used filter and sliding in a new filter. Furnace filters fit in a filter frame located in front of the furnace's air intake. The filter should be the length, width and thickness specified by the furnace manufacturer.

Locate the Furnace Filter

The furnace filter is located at the furnace air intake, which is inside the blower compartment. In an up-flow furnace, which moves air upward, the filter is in the blower compartment next to the cold air return. In a down-flow furnace, which moves the air downward, the filter is located in the upper blower compartment. Furnaces that have a v-shaped filter system require two filters. Horizontal furnaces and air handlers have a rack for the filter to slide into. The front edge of the existing furnace filter will be printed with the dimensions for height, width and thickness. Purchase a replacement filter at a home improvement store.

Changing the Filter

Turn off the power to the furnace at the thermostat by setting the thermostat to "off." Remove the door or cover to the blower compartment, if there is one. Slide the old filter out and bag the dirty filter for disposal. Remove any plastic wrap from the new furnace filter. Locate the directional arrows on the filter. Slide it into position, either on the rack rails or clips, in the direction indicated. Do not force the filter.

Finishing Filter Installation

Reinstall any covers or doors, Manually tighten screws or clips. Make certain that covers re-engage any safety switches. Turn the power by resetting the thermostat to the desired indoor air temperature.

Source:

Furnace Filter Care

Filters USA: How to change your furnace filter

Green Guide: Clean Your Furnace Filter

Open the furnace locate the filter take it out put the new one in close the furnace.