When looking for an air filter for an application, the MERV rating is one of the most prominent qualifications to consider. Depending on the environment the filter will be used in, the MERV rating can play a large role in which air filter you choose. But what exactly does a MERV rating indicate?
MERV stands for ‘Minimum Efficiency Reporting Value.’ MERV filter ratings are on a scale of 1-20 of how effectively a filter traps small particles. The higher the number, the higher the amount of particles the filter traps. It’s important to note that the number represents the filter’s lowest possible performance, not it’s best. It’s a ‘worst case scenario’ of how well the filter can perform.
The American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) established the ranking system in 1987 and it has remained an important way to determine the efficiency of an air filter.
Who Should Use These Ratings?
While most industries or work environments don’t necessarily have requirements for the MERV rating of air filters used, knowing the different particles filtered by each will help you better understand which rating is best for your application.
1-4: The lowest MERV ratings will filter larger particles like pollen, dust mites, sanding dust, and textile fibers. They’re often sufficient for residential areas or applications where there is not a lot of traffic.
5-8: This is typically the rating recommended for an average household and average commercial buildings. They will filter particles like mold, hair spray, and cement dust.
9-12: At this level we begin to see more robust filtration for more specific applications. Filters with these MERV ratings can filter out lead dust, milled flour, auto emissions, and welding fumes to name a few. They are often appropriate for some hospital or healthcare settings, commercial buildings, and industrial applications.
13-16: This is traditionally the highest MERV filter rating for standard air filters. These filters can remove bacteria and tobacco smoke. They can be used in surgical suites, hospitals, industrial settings, and in any other application that requires more robust filtration.
17-20: Filters with these MERV ratings can filter particles < 0.3 microns. This is where HEPA and ULPA filters fall – some of the most efficient filtration for more difficult applications. They can remove viruses and other small particles, making them perfect for clean rooms, laboratories, and spaces dealing with carcinogenics or radioactive materials.
It’s important to keep in mind that a higher MERV filter rating doesn’t always necessarily mean it’s the best filtration for you. For many residential or commercial applications, a lower MERV rating is sufficient for filtration. It’s in environments like healthcare, construction, laboratories, and chemical settings that the MERV rating should be higher.
Higher MERV ratings also have a lower air flow and circulation because they create more resistance. In an industrial or commercial setting, systems are typically in place to atone for this. In a typical house, however, most HVAC systems will not be equipped for a filter with such high resistance. This would mean more energy use and your system and filter will likely wear out very quickly. It’s important to understand which MERV rating will work best for your application.
For more information about our custom filters and MERV ratings, contact APC. We can help you find an air filter that fits your needs!
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