What Do Air Filter MERV Ratings Mean?

Air filters are a crucial line of defense for you and your household and are essential in all heating and air conditioning systems. By filtering particles and microbes out of the air, filters can protect you from dangers and contaminants. Unfortunately, choosing an air filter can seem intimidating due to the variety of options and complex rating system.

This article will explain what air filter MERV ratings mean, how the rating system works, and how you can determine what type of air filter is right for you. By the end of this article, you’ll be fully prepared to choose the right air filter for your home.

If you’d rather leave this up to the pros, we understand, and we can help. If you’re looking for air conditioning tune-up professionals in Chicago, IL, A Custom Services can provide the expert and considerate service you deserve. Whenever you have a problem with the air quality or temperature in your home, you can trust A Custom Services to make things right.


Contaminants in the air can cause harm to you and your household. Dust, pollen, and pet dander in the air can trigger allergies, and those with asthma or other respiratory issues also suffer from poor air quality. With the constant concern of a pandemic looming in our minds, air filters constitute another measure we can take to provide peace of mind.

An effective air filter can improve your quality of life in various ways. When you breathe better, you feel better, so expect more energy and quality sleep with a high-quality air filter. 


Air filters work by passing air through extremely narrow gaps; these gaps allow air through but trap particles floating in the air, resulting in clean air flowing through the other side. An air filter’s MERV rating refers to the size of the airborne particles the filter is capable of trapping, with higher-rated filters trapping much finer pieces of material.

Filters with higher MERV ratings are often used in high-risk environments, such as hospitals and operating rooms. In contrast, lower-rated filters are used when air purification is needed for large spaces.


While reading about MERV ratings might make it seem like you should buy the highest-rated filter possible, there’s a bit more to it. Because smaller filters have smaller passageways for air, it’s more difficult for large quantities of air to flow through them, creating resistance.

Using a filter with resistance that is higher than intended for your system can be problematic. The increased resistance will make your unit work harder and cost you money in maintenance. It can also reduce the performance of your system, making your home less comfortable even when your heater or air conditioner is on.


Here are some general guidelines to follow when determining what level of air filter MERV rating you should target for your desired application:

  • MERV Rating 1-4: This filter level is typically used for smaller-scale applications such as residential furnaces and window-mounted AC units. They also may be used as pre-filters in larger setups.
  • MERV Rating 5-8: This level is ideal for most residential and commercial applications, filtering out contaminants like pollen, mold, and spores. 
  • MERV Rating 9-12: Filters at this rating level provide highly effective air filtration while maintaining a level of resistance that can still be sufficient for larger applications. While the most conscientious homeowners may choose this level, it is primarily used for laboratory and commercial settings.
  • MERV Rating 13-16: Used in operating rooms and as final filters in complex systems, these filters provide superior filtration but are usually overkill for residential applications.
  • MERV Rating 17-20: Finally, the highest-rated air filters offer unmatched efficacy and are almost exclusively used for extremely high-risk environments, including facilities that process radioactive or poisonous materials. Most consumers can safely ignore them.

Other Options

Another option to consider, particularly for those with breathing problems or allergies, is the use of multi-filter systems. In such systems, one filter would be used as the primary filter for the heater or HVAC unit, while one or more other filters would be used as a pre-filter. While this won’t reduce the particle size your system will filter, it will reduce the stress on each filter and increase reliability.


Regardless of what type of air filter you choose, it’s vital to ensure you regularly clean and change your filters as needed. Even when you properly consider the air filter MERV ratings, no air filter can function when clogged with dust and debris, and a dirty filter can be worse than not having one at all. 

A dirty air filter will increase the stress on your refrigerating and air conditioning system, making it more difficult to pull air through the ducts and into your home. Heaters are also susceptible to wear from this increased resistance, so you should call a professional if you think your heating or air conditioning system requires cleaning. While maintenance can be tedious or irritating, you’ll reap the rewards with lowered maintenance costs and a consistently comfortable temperature in your home.

Furnace cleaning and maintenance are also essential for protecting the air quality in your home. A Custom Services is proud to help the Chicago area stay warm through the winter by ensuring their furnaces are well maintained and promptly repaired. If you’d like to learn more about heating services offered by A Custom Services, call 773-831-4891 to speak with a friendly staff member. 


Now that you’ve finished this article, you know everything you need to start improving your indoor air quality today. Whether you know precisely what air filter MERV rating you need for your Chicago home or business, or you’re still a little confused, A Custom Services is happy to work with you to resolve your indoor air quality concerns.

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