Determining the right MERV rating for your furnace filter can be tricky. There are various types of filters to choose from, and it might be hard to select a filter that best suits your needs. We’re here to help. Norrell Service Experts is your local HVAC Expert in Birmingham, helping you make smart decisions for your home.
Getting the right furnace filter is all about balancing indoor air quality with your HVAC system’s capabilities. Getting filters with the right MERV ratings is critical to ensuring your air is healthy without overworking your HVAC system.
What Does MERV Mean?
A minimum efficiency reporting value, or MERV is a rating system designed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). MERV ratings signify an air filter’s effectiveness at reducing airborne particles and contaminants. A filter’s rating is determined by the minimum size particle it’s capable of trapping (measured in microns). As filters become better at improving indoor air quality, their MERV rating goes up, ranging from 1 to 20.
Below, you will find a chart that can help you determine the necessary MERV rating for a variety of applications.
| MERV Range | Controlled Contaminants | Typical Application | Air Filter Types |
| 1-4 | Pollen, Dust, Spray Paint, Dust Mites, Sanding Dust, Textile & Carpet Fibers | Residential, Window AC Units | Disposable Electrostatic |
| 5-8 | Mold Spores, Pet Dander, Hair Spray, Dusting Aids, Fabric Protector, Cement Dust, Pudding Mix | Better Residential, Commercial, Industrial Workplaces | Pleated Filters Cartridge Filters Electrostatic |
| 9-12 | Legionella, Auto Emissions, Lead Dust, Humidifier Dust, Welding Fumes | Superior Residential, Better Commercial, Hospital Labs | Pleated Filters Cartridge Filters |
| 13-16 | Bacteria, Droplet Nuclei (Sneeze), Tobacco Smoke, Insecticide Dust | General Surgery, Hospital Inpatient Care | Bag Filters Box Filters |
| 17-20 | Viruses, All Combustion Smoke, Carbon Dust | Cleanrooms, Radioactive & Carcinogenic Materials, Pharmaceutical Manufacturing | HEPA Filters Specialized Filters |
Other Measurement Systems
Knowing about MERV ratings might not be enough when the time comes to purchase your furnace filter. For example, some major retailers use the filter performance rating (FPR), which ranges from 1-10 and measures a filter’s ability to capture large and small particles. You might also see the microparticle performance rating (MPR) system, which goes from 300 to 2200 and measures a filter’s effectiveness at capturing only the smallest particles on the MERV scale (0.3-1 microns in size).
You can use the chart below to better understand how filters ranked with FPR and MPR stack up to the more standard MERV rating system.
| MERV Rating | FPR | MPR |
| MERV 1-5 | Below Minimum FPR | Below Minimum MPR |
| MERV 6 | Below Minimum FPR | MPR 300 |
| MERV 8 | FPR 5 | MPR 600 |
| MERV 11 | FPR 7 | MPR 1000-1200 |
| MERV 13 | FPR 10 | MPR 1500-1900 |
| MERV 14-20 | Above Maximum FPR | MPR 1900+ |
What Should My Furnace Filter’s MERV Rating Be?
Choosing the right MERV rating for your air filter is a balancing act between your HVAC system’s capabilities and the indoor air quality you want to achieve.
For example, a better MERV rating doesn’t always mean that a filter is the right option for your furnace. In fact, as MERV rating goes up, air flow goes down—forcing your HVAC system to work harder to push air through your furnace, increasing the likelihood of a potential breakdown. Before buying a new furnace filter, be sure to check if your HVAC system has a limit for MERV rating. If it does, be sure to buy a furnace filter with a MERV rating that’s lower than your system’s maximum.
If your family has allergies or serious respiratory issues like asthma, you may want to invest in filters with higher MERV ratings. Remember, there are always other options available to improve your indoor air quality if your system is unable to handle the MERV ratings you require.
Generally speaking, our recommended MERV rating for furnace filters runs from 6 to 8 for a great balance between top furnace efficiency and home comfort.
Choosingthe right MERV rating for your furnace filter has a huge impact on your indoor air quality, your HVAC system and, most important, your family’s health. Let Norrell Service Experts help you make a smart decision. We have a complete line of air filtration solutions plus our Expert knowledge and service—and we’re available 24 hours a day for emergencies. Contact us at 866-397-3787 to schedule your indoor air quality consultation in Birmingham today!