Where Is My Air Filter?

If you didn’t know your forced air system had an air filter—or if you’re not sure where it is—this article is for you.

In homes across Central Massachusetts, we see filters installed in a variety of places. Knowing where yours is located—and how to check or change it—is the single most important thing you can do as a homeowner to protect your HVAC system.

Let’s go over the most common locations.

📍 Common Air Filter Locations

1. Filter Grille (Wall or Ceiling Return)

• Found on a large grille in the wall or ceiling

• Has tabs or screws to open the panel

• Filter is typically 1 inch thick

• Easy to access—great for regular homeowner replacement

2. Filter Cabinet Near Furnace or Air Handler

• Located in a metal box beside or below your furnace or air handler

• May have a pull-out drawer or cover panel

• Filters in these cabinets are usually 2 to 5 inches thick

• Often used for high-efficiency filtration systems

3. Inside the Furnace Cabinet

• Requires removal of the front panel on the air handler or furnace

• Filter is typically 1 inch thick

• Not always easy to access—best to ask your technician to show you

4. Inside the Ductwork

• Found in or near the return duct, usually close to the air handler

• These are often custom installs—placement varies widely

• Some locations are awkward and hard to reach

• Not ideal, but still common in older or DIY systems

🧠 A Few Important Notes

• Filter sizes vary widely. A quick walk through Home Depot will show you just how many options there are.

• Many homes have more than one filter, especially if they have systems upstairs and downstairs.

• While most systems have one filter per central fan, that’s not a guarantee—always ask your technician to point out all your filters during a visit.