Short answer: The arrow on the furnace filter should point toward the furnace, i.e., in the direction of the air flow from the return duct into the furnace. Details to ensure correct orientation and fit:
- Airflow direction: In a typical residential system, air moves from the return ducts into the furnace or air handler, then onward to the supply vents. The filter should be installed so air flows through it in that same direction (return → filter → blower). This means the filter’s arrow should point toward the furnace/blower.
- Where to look for the filter: Common locations include a slot in the return air duct opening, a slot in the furnace/air handler cabinet, or a side-mounted slot on horizontal units. The orientation rule remains the same regardless of location.
- Fit and seal: Use the correct filter size for the slot and ensure there are no gaps around the edges. A snug fit improves filtration and reduces air bypass.
- Special notes:
- If your system uses a disposable panel with multiple slots, follow the arrow orientation for each slot.
- If you’re unsure where the arrow should point, locate the return air path and align the arrow to move air toward the blower.
If you’d like, share the model of your furnace or the location of the filter slot (return grille, cabinet slot, or side slot), and a quick, step-by-step installation guide can be tailored to your setup.
