Air Filter Basics: What Every Homeowner Should Know 

What Does an Air Filter Actually Do?

Your air filter sits where air enters your heating and cooling system. As air passes through, the filter traps airborne particles, keeping them out of your living spaces and out of the system’s sensitive components. The result is cleaner air to breathe and an HVAC system that runs more efficiently.

A clogged or low-quality filter forces your system to work harder, which can raise energy bills and shorten equipment life. A clean, well-matched filter does the opposite.

Understanding MERV Ratings

MERV (Minimum Efficiency Reporting Value) tells you how effectively a filter captures particles, on a scale from 1 to 20. Higher numbers catch smaller particles.

• MERV 1–4: Basic protection, mostly for large particles like lint and dust.

• MERV 8–11: A strong choice for most homes—captures dust, pollen, mold spores, and pet dander.

• MERV 13+: Captures finer particles, including some bacteria and smoke. Great for allergy-sensitive households, but check that your system can handle the airflow.

Higher isn’t always better for every system. A filter that’s too dense for your equipment can restrict airflow, so it’s worth matching the rating to your HVAC’s specifications.

How Often Should You Change Your Filter?

A practical rule of thumb: check it monthly and replace it every 1–3 months. Homes with pets, allergies, or heavy use will land on the shorter end of that range. Hold the filter up to the light—if you can’t see through it, it’s time for a new one.

Choosing the Right Size

Filter size is printed right on the frame of your current filter (for example, 16x25x1). Matching that exact size matters: a filter that doesn’t fit snugly lets unfiltered air slip right past it.