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Air filter ratings were established by the HVAC industry to provide consumers with a frame of reference. Ideally, a consumer would be able to compare the rating of one product to another in order to decide which is preferable. In practice, ratings often cause consumer confusion. This is because there are multiple rating systems. It is often unclear what the ratings mean, and the purpose of a filter often dictates the optimal rating. With all this in mind, we will present to you some of the most common questions we receive about air filter ratings along with concise answers to clear up any confusion.

What Is MERV Rating?

MERV is an acronym for minimum efficiency rating value. It was introduced in 1987 by ASHRAE—a trade association. This rating system ranges from 1 to 20, but ratings above 16 are often not used as those products are typically sold under specific certifications, such as HEPA. Air filters with a MERV 1–4 are suitable for pollen and dust mites. A MERV 5–8 air filter is appropriate for pet dander and mold spores. MERV 9–12 air filters can trap auto emissions and Legionella, and MERV 13–16 air filters allow for trapping bacteria and droplets from sneezing. While other systems exist now, MERV was an important breakthrough in rating air filters with precision.

Is Too High or Too Low a MERV Rating Bad?

Yes, a rating that is too high or too low can be bad. It is important to note that the higher the MERV rating, the higher the resistance and lower the airflow. When it comes to air cleaners, the higher the MERV rating, the better. However, if an air cleaner is not powerful enough to overcome a resistance above MERV 8, for instance, then an air filter with a higher rating would diminish performance. This is the case with HVAC intakes as well. Those returns are designed to block dust from getting into the system rather than clean the air. Restricted airflow can reduce energy efficiency, increase costs and result in undue wear and tear.

What Is MPR?

MPR stands for micro-particle performance rating. This is a rating system developed by the company 3M specifically to rate filters based on their ability to trap particulates between 1.0 and 0.3 microns in size. The MERV system, on the other hand, focuses on larger particles. The MPR system is only useful when comparing filters that are all rated based on this system. As of this writing, 3M is still the only company using it. While 3M is a major company in the air filter world, this system lacks value in terms of easily comparing filters made by different manufacturers.

What Is FPR Rating?

FPR stands for filter performance rating. This system was developed by The Home Depot, a home improvement retail chain. It uses a scale that ranges from 4 to 10, and each rank has a dedicated color associated with it for easy visual identification. It is limited to products available in The Home Depot store. However, The Home Depot is a big company with a lot of purchasing power. So, while it adds FPR to its own branded products, this designation also appears on products from other manufacturers if The Home Depot carries them and the packaging has been specifically designed for their stock.

What Is the Difference Between MERV, MPR and FPR?

MERV, MPR and FPR are the three most widely used air filter rating systems in the United States. While these systems are not designed for cross-comparison, it is still possible to do. There are even premade charts used in retail shops and by HVAC technicians. MERV 6, for instance, is comparable to MPR 300. MERV 8 correlates to MPR 600 and FPR 5. MERV 11 is equivalent to MPR 1000–1200 and FPR 7, while MERV 13 is like MPR 1500–1900 and FPR 10.

Is HEPA an Air Filter Rating?

HEPA stands for high-efficiency particulate air, and it refers to a set of standards. HEPA air filters are both tested and certified. Note that HEPA-like and HEPA-type filters have either not been tested or have failed the certification process. True HEPA is a rating in the sense that you can depend on a basic HEPA filter to remove 99.97% of all particulates that are at least 0.3 microns in size. Many HEPA products do not post MERV, MPR or FPR ratings. The HEPA designation is an attempt to make a product’s performance clearer to the consumer. It is presumed that most HEPA products are at MERV 17 or above.

What Is the Difference Between HEPA and Medical-Grade HEPA?

There aren’t actually various types of HEPA. There are, however, certain filters that test at a higher level of efficiency. The term medical grade refers to a higher standard. True HEPA is H10 to H12. Medical-grade HEPA refers to H13 and above. These can trap between 99.99% and 99.995% of all particulates at least 0.3 microns in size. Such filters are used in certain hospital scenarios, during pharmaceutical manufacturing and in electronic control rooms. They are not generally meant for home use.

What Rating Do You Need for the HVAC Return Air Filter?

Usually, a MERV rating of 8 is adequate for your HVAC system’s filter. A lower rating will work as well but will not filter as many particulates. A higher MERV rating may also be suitable up to a point. HEPA filters are generally too much for HVAC systems. If you’re considering a MERV rating higher than 8, be sure to check the manufacturer’s specifications, and be aware that it may be possible to void your equipment warranty.

Which Rating Is Best for an Air Cleaner?

Since you can undermine performance if the airflow is restricted too much, you should check the manufacturer’s recommendations for your unit. Within the allowed range, higher is better. Many of the most popular air cleaners on the market are designed for use with HEPA filters, which are at the high end of the MERV rating scale.

Do Washable Filters Become Less Effective Over Time?

Many consumers wonder if the rating of a washable air filter changes over time, and the answer is that it does not—at least in theory. You should purchase a high-quality washable air filter from a manufacturer you trust. It is also essential that you wash the filter according to the manufacturer’s recommendations. This is where many people go wrong, and it’s the strongest argument against such filters. You must be committed to washing them regularly, or their performance will not reflect the rating at the time of purchase. You must decide if that extra effort is worth the savings.

Let Us Answer Your Air Filter-Related Questions

Summit Heating & AC is proud to have served Denver and the surrounding areas for more than 20 years. We have NATE-certified technicians on staff, offer affordable prices and free estimates and provide a 100% satisfaction guarantee. We also sell high-quality air filters. Our team installs, maintains and repairs home air cleaners, air purifiers as well as heating, cooling and ventilation systems. We even offer maintenance agreements that will help you save and ensure your home’s air filters are always clean. Call us today at Summit Heating & AC to ask any questions about air filter ratings or to schedule your first appointment.