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What Do MERV Ratings Mean?

04/26/17

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Have you ever taken a close look at your HVAC filters when replacing them? If so, you may have noticed that each filter has a MERV rating -- and this number has important implications.

MERV stands for “minimum efficiency reporting value” and the MERV rating is a measure of how effectively a filter removes particles from the air that passes through it. The higher the MERV rating, the more particles the filter will catch.

There’s a flipside to this, though. Filters with higher MERV ratings generally feature denser filtration material, which means more force is required to push air through the filter. It takes exceptionally powerful HVAC fans to effectively push air through the filters at the high end of the MERV rating scale.

Find Your Number

If you use a filter with a too-high MERV rating in your home HVAC system, it could have the effect of using a dust-clogged filter -- air struggles to push through, which puts accelerated wear on your system’s fan and other components. This leads to more frequent service and repairs.

To make more thoughtful decisions about what type of filter to use in your home HVAC system, start by checking your system’s documentation for a maximum MERV limit. Using filters above the MERV limit will hurt your energy efficiency immediately and will likely cause more expensive problems down the line.

Once you know your available range of MERV ratings, consider whether there are signs you might need more filtration than you currently enjoy. Are there allergy or asthma sufferers at home? Do you have a shedding pet? Does your home seem abnormally dusty? If the answers to any of these questions is yes, you may be able to find some relief by upgrading to a filter with a higher MERV rating.

By The Numbers

MERV ratings range from 1 to 20. In residential HVAC systems, filters in the 1-4 range are most common, but it’s not unheard of for homeowners to use filters with MERV ratings as high as 8 in typical household systems.

Here’s a quick rundown of what filters of various MERV ranges are capable of filtering out of the air:

MERV 1-4

These filters catch large particles: dust, dust mites, pollen, carpet fibers, insects and some of their waste. They’re primarily used in residential HVAC systems.

MERV 5-8

These filters are used in some homes and in most commercial and industrial settings. They can catch finer dust particles, mold spores, aerosol spray particles and pet dander.

MERV 9-12

Rarely used in residences, these filters are common in certain commercial buildings and in some hospital laboratories. They can capture automotive emissions, welding fumes, lead dust and larger bacteria.

MERV 13-16

These heavy-duty filters are typical in hospital surgical centers and other areas where heavy filtration is paramount, such as smoking lounges. They collect a larger range of bacteria, smoke particles, oil droplets and fine particles from sneezing.

MERV 17-20

At the top of the scale, these filters are used in clean rooms where pharmaceuticals and sensitive electronics are produced. They can catch viruses, carbon dust and the smallest smoke particles.

You’ll probably never need to use those filters at the top of the MERV rating list, but whenever you take a pill or fire up your computer, you’re benefiting from their filtration capabilities. Curious about what type of filter you should be using at home? Call your local HVAC professionals for expert advice.



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