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How To Choose A Furnace Filter and When to Replace It

How To Choose a Filter and When to Replace It

There are many benefits to having filters. You can improve your indoor air quality, keep your home clean, lower your energy bill, relieve your allergies, etc. Air contaminants can greatly effect your health–so, stay healthy! With a good filter, you can enjoy better air flow, less

Choosing a filter can be a troubling task–which one do I want? Which is best for pets? What do these letters stand for? What if I suffer from allergies? How often should I change them? We just changed ours after 2.5 years (oops! See photo to the left) and let me tell you, it is night and day! The before-and-after photos are clearly black and white. 


There are 3 rating systems that you should know about:

MERV (Minimum Efficiency Reporting Value– this is used worldwide and rates a filter by how well it can capture pollutants and small particles. The higher the number, the better it is (highest being 13).

MPR (Micro-Particle Performance Rating) — this rating system was created by 3M, one of the major manufacturers and how well the filter can catch airborne particles (smaller than 1 micron) and the ratings range from 300-1900.

FPR (Filter Performance Rating) –The Home Depot created this system and contains a color and number scale that mimics the MERV rating.

For smoke, smog, pet dander — opt for MERV 11, MPR 1200, FPR Red 7

For dust mites & mold — opt for MERV 8, MPR 600, FPR Green 5

For dust, lint, and indoor pollen — opt for MERV 6 or MPR 300

Make sure that you measure the filters that you are replacing to ensure a match. The thickness of a filter impacts its efficiency and ability to remove contaminants. There are two standard filter thicknesses, 1″ and 4″. If your system uses a 1” filter, a 4” filter will not be able to fit the existing cabinet. In general, the  more pleats means the more it can capture.

How often should I replace it?

Replace your furnace filters regularly to improve indoor air quality while lowering your energy bill and keeping your home clean. Every quarter, consider changing the filters. However, if your goal is to rid indoor dust/pollen/lint, consider changing it out on a monthly basis or whenever it gets dirty. When in doubt, remove the filter and clean it out manually with a toothbrush. Just don’t wait 2.5 years like we did!

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Michelle Chan

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