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How Do MERV Ratings Work?

an image of an air quality technician with a hard hat on holding on to an air filter.

Air quality is one of the hottest topics in the news. Wildfires are raging in Canada, and winds are pushing the smoke south toward more populated areas like Ontario.

Health advisories are instructing Canadians to stay indoors. Your HVAC system is an important tool in this fight as it blocks air pollutants from circulating in your home.

Your air filter needs to be clean and have high-performance ratings to keep up with this demand. Read on to learn how MERV ratings work. Explore topics such as minimum efficiency reporting values and how to improve indoor air quality.

What Does an Air Filter Do?

Before diving into a filter's MERV rating, it is important to under what they do. Your HVAC system's air filter is designed to catch particles that would otherwise recirculate throughout the house.

The primary function of the filter is to improve air quality. Dust and airborne mould spores are two of the most important contaminants to filter out. Allergens, pet dander, and other airborne particles can also be stopped with a filter.

Air filters serve other practical purposes in your home. By keeping your HVAC performance at an optimal rate, they lower monthly energy costs. Your HVAC needs to work harder with a clogged filter and stay on longer.

Also, clean air filters extend the service life of your HVAC unit. Less demand on the system allows components to stay fresh. The end result is an HVAC unit that meets and exceeds its expected service life.

What Are MERV Ratings?

MERV is an acronym that stands for minimum efficiency reporting values. The term was coined by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE).

The rating is determined by vigorous industry testing. A MERV rating indicates how good the air filter is at capturing airborne particles at the micron level. A higher MERV rating means that the filter can capture even smaller air particles.

The lowest possible MERV rating is 1-4. The highest numeric rating is 16; however, there is a high-efficiency particulate air filter (HEPA) that is the industry's best.

At the 1-4 rating, the air filter captures particles that are 3.0 to 10.0 microns. However, they are successful less than 20% of the time.

A level 8 filter can capture particles 1.0 to 3.0 microns large at a 20% efficacy. Their success rate at capturing 3.0 to 10.0-micron particles increases to 70%.

At level 11, the filter is now capable of capturing 0.3 to 1.0-micron particles. The efficacy of larger particles increases for each higher-rated filter.

Level 16 air filters are 95% effective for particles as small as 0.3 microns. HEPA filters are even better, capturing these particles 99.97% of the time.

Your Guide to the Air Filter Rating System

You now have an understanding of what MERV rating is best. This will help when you are shopping for air filters to block indoor contaminants.

Buying a more expensive air filter is worth the investment. Your family is going to breathe healthier air, and your HVAC system is going to last longer.

If you have questions about MERV ratings, contact us today to speak with a professional at Kingston Home Heating and Air.


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