Home Improvement

Understanding MERV Ratings: What They Are and How They Work

Selecting an air filter tailored specifically to your requirements is key to improving air quality in your home. You’ve probably noticed that filters come with different MERV ratings, but what do those numbers actually mean? In this article, we’ll explain MERV ratings and how they work, so you can make an informed decision when selecting an air filter.

What Are MERV Ratings?

MERV stands for Minimum Efficiency Reporting Value. It’s a system used to measure the effectiveness of an air filter at capturing and removing particles from the air. MERV ratings range from 1 to 20, with higher numbers indicating better filtration performance.

How Do MERV Ratings Work?

The scale takes into account particles with sizes ranging between 0.3 to 10 microns. As an illustration, an average human hair measures around 70 microns in diameter. Filters with higher MERV ratings can capture smaller particles than those with lower ratings. For example, a filter with a MERV rating of 8 may capture pollen and dust mites, while a filter with a MERV rating of 13 may also capture mold spores and pet dander.

Factors That Affect MERV Ratings

It’s important to note that not all MERV ratings are equal. A filter with a MERV rating of 13 may capture smaller particles than one with a rating of 10, but other factors can affect overall filter quality. Here are some factors that can impact a filter’s MERV rating:

  • Filter thickness: Thicker filters can capture more particles but also restrict airflow more than thinner filters.
  • Filter density: Filters with higher densities can capture smaller particles but may also restrict airflow more than less dense filters.
  • Airflow rate: Filters that allow for higher airflow rates may not capture as many particles as filters that restrict airflow more.
  • Filter material: Different filter materials have different filtration efficiencies. Pleated filters, for example, generally have higher MERV ratings than flat panel filters.
  • Filter construction: Filters with more pleats or electrostatic charge can capture more particles than those without these features.

Choosing the Right MERV Rating for Your Needs

When selecting an air filter, it’s essential to consider your requirements. If any members of your household suffer from allergies or asthma, an air filter with an increased MERV rating might be needed to protect them. However, a higher MERV rating can also result in reduced airflow and increased strain on your HVAC system. If you need assistance selecting an ideal MERV rating, seek guidance from an HVAC expert or your system owner’s manual. MERV ratings of 8 to 13 are generally suitable for most residential and commercial applications.

It’s also important to note that regular filter replacement is crucial to maintaining good indoor air quality. Even the best air filters will become clogged with particles over time and lose their effectiveness. Filters should typically be changed every 90 days, but this timeline can fluctuate based on factors like the number of residents in your home and any pets present.


MERV ratings are an important consideration when selecting an air filter. They indicate a filter’s ability to capture particles of different sizes, with higher ratings indicating better filtration performance. However, other factors, such as thickness and density, can influence filter quality. By understanding MERV ratings and considering your specific needs, you can choose an air filter that will help improve your indoor air quality.


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