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What is the MERV Rating of an Air Filter?

air filter

There are many different air filters on the market, all of which have varying effects on particle control and air flow. So how are St. Louis area homeowners supposed to figure out which type of filter is right for their homes?

Luckily, the HVAC industry uses a rating system, called a MERV rating, to determine the efficiency of air filters. So what is a MERV rating and how can you use it to choose the filter that’s right for your unit?

What is a MERV rating?

MERV stands for Minimum Efficiency Reporting Value. It is a measurement scale designed by the American Society of Heating, Refrigeration and Air Conditioning Engineers and is accepted as our industry’s standard scale for comparing air filters.

Air filters are assigned MERV values according to how well they can remove airborne particles from your home’s air. On a scale of 1-16, filters with low MERV values can only remove a small percentage of the largest particles in your air, while filters with high MERV values can remove a large percentage of the smaller particles in your air.

How is a MERV rating determined?

To determine the MERV rating of an air filter, a particle generator is used to send various sizes of particles through the filter. A particle count is taken from the air before and after it is sent through the filter. By comparing the two particle samples, we can determine how good the filter is at removing large and small particles from the air.

What MERV rating is best for your HVAC unit?

It might seem like the best decision would be to use a filter with the highest MERV rating. However, you have to remember that filters that are better at blocking out particles are worse for your unit’s air flow. In order to achieve maximum air flow and particle control, use a filter with the highest MERV rating that your unit can handle. This information is often included with your unit when you purchase it.

If you have any questions about a MERV rating, or if you’d like to purchase a filter from a professional contractor, contact Jerry Kelly, your St. Louis heating and cooling company.