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MERV Ratings – By the Numbers


MERV ratings – every furnace filter has one and, depending on the number, it can indicate a vast difference in how efficiently your air filter is working. MERV stands for Minimum Efficiency Reporting Value and is a value used to give an accurate description of air filter efficiency. This scale was designed by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) to rate the effectiveness of air filters. If you are wondering which MERV rating is right for you, the answer is unfortunately not that simple. When it comes to MERV ratings, a higher-rated filter does not necessarily indicate a better filter.

MERV Definition

Ratings are giving to a filter to describe the worst-case performance of the filter media when encountering particles at a specific size. Higher-rated furnace filters capture a higher percentage of particles.  The scale ranges from 0.3 to 10 micrometers with lower-rated filters designed to capture larger particles and higher-rated filters designed to capture the smallest particles.  Deciding which filter is best for you depends on your indoor environment.

MERV Rating 1-4 – Particle Size: >10 μm

On one end of the scale, filters with this rating will obstruct basic particles.  These filters offer only minimal filtration, but can prevent particulates including pollen, dust mites, textile fibers, and carbon fibers from entering your indoor air supply.  These filters are typically used in residential window A/C units.  Air filters with a MERV rating of 1-4 typically do not do an effective job of removing all airborne pathogens.

MERV Rating 5-8 – Particle Size: 10.0-3.0 μmhome air filter

Filters within this range are suggested for everyday home filtration.  They block particles smaller than that of the 1-4 range including pollen, pet dander, dust mites, lint, and mold spores.  Furnace filters with a MERV rating of 5-8 can be found in standard residential areas, commercial buildings, and many industrial workplaces.  To do an efficient job of removing airborne pathogens in your indoor living spaces, an air filter with at least a rating of 5-8 is recommended.

MERV Rating 9-12 – Particle Size: 3.0-1.0 μm

If you need a more controlled environment, or suffer from allergies, you should consider investing in an air filter with a MERV rating of 9-12.  These air filters have the capacity to block smaller particles such as humidifier dust, lead dust, smog, odor, and legionella. The effectiveness of filters in this range make them ideal for superior residential building, better commercial buildings, and even hospitable laboratories. Try a filter in this range for a more sterile indoor environment.

 

MERV Ratings

MERV Rating 13-16 – Particle Size: 1.0-0.3 μm

For indoor environments where more controlled air quality is necessary, filters with the MERV rating within the 13-16 range will do the job.  With the ability to block tiny particles such as bacteria, insecticide, smoke, most paint pigments, and droplet nuclei found in sneezes, these filters are ideal for people who experience respiratory issues such as asthma.  These filters are not typically found in residential buildings.

MERV Rating 17-20 – Particle Size: <0.3  μm

For indoor spaces where sterile environments are absolutely critical, filters in this MERV range are required.  Particles including viruses, sea salt, carbon dust, and smoke are all captured by the filter media in this category.  Pharmaceutical and electronic manufacturing companies utilize these filters to provide a sterile environment for their manufacturing cleanrooms where a sterile workspace is crucial.

The Environmental Protection Agency of the United States recommends medium efficiency filters for residential buildings. Filters between the ranges of 5-13 do a reasonably efficient job of removing airborne particles, but we recommend using a filter with a MERV rating of at least 8. The highest recommended range for residential systems is 9-12. Because the pores allowing for air flow in a highly-rated MERV filter are very small, the filter creates more resistance against air flow and may put too much pressure on the fan of your furnace or air conditioning unit. It’s important to choose an air filter with the highest MERV rating that your particular unit will allow for maximum air flow. Information about specific MERV ratings and recommendations for your furnace will generally be included with the documentation that came with your system.

Remember to change your air filters about 4 times a year to ensure high quality effectiveness in reducing the particles in your indoor air. Discount Air Filters has a wide selection of filters for your specific size and desired MERV rating. As always Discount Filters offers free shipping and returns on all discount air filters and refrigerator water filters.

3 thoughts on “MERV Ratings – By the Numbers”

    • This is true. The highest recommended range for residential systems is 9-12. Because the pores allowing for air flow in a highly-rated MERV filter are very small, the filter creates more resistance against air flow and may put too much pressure on the fan of your furnace or air conditioning unit.

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