How to Know Which Direction the Arrow Means on a Furnace Filter for the Home

Changing the filter in your furnace is one of the best ways to ensure the long life of your furnace. This appliance is quite expensive, therefore proper maintenance is essential to keep it running efficiently. Changing the filter is not difficult, but it must be done with the arrow on the filter pointing in the right direction. Some filters are washable, but disposable filters require changing every one to three months depending on what brand you buy. This also helps keep the air circulating in your home clean and less polluted with dust, pollen, mold or smoke.

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Some furnaces are located in basements or attics.

Up-Flow Furnace

Step 1

Turn off your furnace at the main circuit breaker. This prevents the unit from coming on while you are replacing the filter.

Step 2

Locate the filter in the bottom door next to the cold air return in your up-flow furnace.

Step 3

Remove the top door first and then take out the bottom door.

Step 4

Pull out the dirty filter and take note of which way the arrow is facing when removing it. This is the direction the arrow on the new filter must face. The arrow must always point toward the blower motor or furnace -- this is the large section of the furnace.

Step 5

Slide the new filter in with the arrow facing the blower motor or furnace.

Step 6

Replace the top door and then the bottom. Check that the bottom door goes over the furnace frame. This action engages the safety switch. Neglecting to do this results in a furnace that won't run.

Step 7

Turn the furnace back on at the main circuit breaker.

Down-Flow Furnace

Step 1

Turn off your furnace at the main circuit breaker. This prevents the unit from coming on while you are replacing the clean filter.

Step 2

Locate the filter in the upper compartment of the blower. Down-flow furnaces require two filters.

Step 3

Remove both doors, starting with the one on top.

Step 4

Slide out the dirty filters and replace them with the new ones. Take note of which way the arrows face when replacing the filters and install the new ones in the same fashion, but always facing the blower motor or furnace. The filters fit in a V-shape in the space.

Step 5

Replace the top and then the bottom door. Make sure the bottom door fits securely over the furnace frame to engage the safety switch.

Step 6

Turn the furnace back on at the main circuit breaker.