MERV Ratings: What Do They Mean?

A home’s indoor air quality (IAQ) directly impacts the comfort and health of the household’s residents. Two of the easiest ways to maintain suitable indoor air quality are regularly replacing your air filter and ensuring you’re using an air filter with an appropriate MERV rating. While most people know they have to periodically replace their air filters, not as many people know what a MERV rating is — let alone what rating they should be using. With that in mind, our trusted HVAC company has compiled a guide detailing everything a person needs to know about air filter MERV ratings.

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What Is MERV Rating?

An air filter’s Minimum Efficiency Reporting Values, or MERV rating, refers to how effectively a filter captures dust particles and other contaminants, stopping them from passing through the filter and into the air. MERV ratings range from 1–20, with higher ratings trapping smaller particles more effectively than lower ratings. Nowadays, a filter’s MERV rating will be listed somewhere on its packaging.

Understanding Different MERV Ratings

The higher the MERV rating, the more efficient the air filter is at stopping small particles from entering the air stream. The following list outlines the differences between MERV ratings.

MERV Rating 1–4

A filter with a MERV rating of 1–4 is only effective at capturing particles larger than 10 micrometers. Filters with this MERV rating are commonly used in residential furnaces, window air conditioner units, and pre-filtered commercial buildings. Filters of this rating will capture particles such as pollen, dust mites, and household debris like carpet fibers.

MERV Rating 5–8

Air filters with a MERV rating of 5–8 capture particles larger than 3 micrometers and are commonly used in commercial, residential, and industrial buildings. In addition to capturing everything a filter with a lower rating can, filters with a 5–8 rating are effective in capturing pet dander, mold spores, and concrete dust. Generally, a MERV rating of 5–8 is the baseline for most household-installed HVAC systems’ filters. 

MERV Rating 9–12

Filters with a MERV rating of 9–12 capture particles as small as 1 micrometer and are commonly used in hospital laboratories as well as residential and commercial buildings that require greater air quality.  In addition to capturing everything, a filter with a lower rating can, filters with a 9–12 rating effectively capture legionella, lead dust, and automobile emissions. 

MERV Rating 13–16

Filters with MERV ratings between 13–16 are often reserved for use in buildings that require exceptional air quality, such as surgical centers and inpatient care facilities, capturing particles as small as 0.3 micrometers. A filter of this rating can capture bacteria, sneeze droplets, smoke, and more.

MERV Rating 17–20

Commonly used in pharmaceutical facilities or buildings housing radioactive and carcinogenic materials, filters with a MERV rating of 17–20 can capture particles of virtually any size, including virus carriers, microscopic allergens, carbon dust, and more. 

What MERV Rating Is Right For Me?

Although higher MERV ratings are more efficient at capturing smaller particles, air filters with excessively higher MERV ratings are not always better for your HVAC system. If you use a filter with a higher MERV rating than is recommended by manufacturers, it can damage your furnace or air conditioner. As stated above, a MERV rating of 5–8 is typically recommended for permanently installed residential HVAC systems. However, if a person suffers from severe allergies or other health issues, they may want to consider upping their MERV rating.