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MERV ratings – every furnace filter has one and, depending on the number, it can indicate a broad difference in how efficiently your air filter operates. Designed by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE), MERV stands for Minimum Efficiency Reporting Value and rates the effectiveness of air filters. 

If you’re 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.

Ratings are given 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 the lower end of the scale, filters with this rating will stop basic particles. Most commonly used in window A/C units, these filters offer minimal filtration but can prevent particulates from entering your indoor air supply, including pollen, dust mites, textile fibers, and carbon fibers. Air filters with a MERV rating of 1-4 typically do not effectively remove all airborne pathogens.

MERV Rating 5-8 – Particle Size: 10.0-3.0 μm

Filters within this range are recommended for simple home filtration. They block particles smaller than ones in the MERV 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 typical residential areas, commercial buildings, and many industrial workplaces. An air filter with at least a rating of 5-8 is recommended to do an efficient job of removing airborne pathogens in your indoor living spaces.

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

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

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 microscopic 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 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 manufacturing cleanrooms where a hygienic workspace is crucial.

The Environmental Protection Agency (EPA) 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 airflow 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. Choosing an air filter with the highest MERV rating that your particular unit will allow for maximum airflow is essential. 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 four times a year, or monthly if you have pets, to ensure high-quality effectiveness in reducing the particles in your indoor air. 

At Discount Filters, we have a wide selection of filters for your specific system size and desired MERV rating. Get free shipping on orders over $50 and save an extra $5 when combining air and water filters!