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Why Change your Furnace Filter? Two Good Reasons

By Kristen Bailey

The air filter in your furnace is often overlooked, but its contribution to your indoor air quality and the efficiency of your HVAC system can’t be overstated. Your air filter prevents the buildup of dust and other particles on your furnace’s fan and heat exchanger, which can significantly reduce its efficiency by making it work harder to keep your home warm.

Dust buildup can cause your system to overheat, which may result in a cracked heat exchanger and expensive repair bills.

In addition to protecting your furnace and improving its efficiency, your air filter also helps improve your indoor air quality. Particles in the typical home include dust, dust mites, pollen, mold, animal dander and bacteria. Your furnace filter traps many of these particles to help you breathe easier and prevent allergy and asthma attacks.

Air filters are given a rating on the 16-point Minimum Efficiency Reporting Value, or MERV, scale. The higher the MERV rating, the better the filter will perform, trapping more and smaller particles.

Before upgrading your furnace filter to one with a higher MERV rating, check the specs of your furnace. Filters with high MERV values are denser and thicker and can impede the flow of air to some systems, causing the unit to overheat.

MERV 1-4

Filters are very inexpensive and won’t do much to improve your indoor air quality. Because they trap only particles larger than 10 microns, these filters should be avoided.

MERV 5-8

Filters are of medium quality, trapping particles such as mold sporesdust mite debris and animal dander. These filters are sufficient for most households.

MERV 9-12

Filters are of higher quality and are ideal for households with allergy and asthma sufferers, trapping very small particles such as lead dust and other fine particulates.

MERV 13-16

Filters are of the highest quality. Generally only used in commercial buildings, these filters trap the smallest particles, such as bacteria and smoke.


Check your filter every month and replace it when it’s dirty. Changing the air filter is a simple task. The filter is generally located in the blower compartment between the cold-air return and the furnace. The filters slide in and out easily; just make sure the arrows on the filter frame are pointed toward the furnace, in the direction of the airflow.



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Disclaimer: Articles not intended to Diagnose, Treat, Cure or Prevent Diseases.

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