MERV ratings are used to rate the ability of an air conditioning filter to remove dust from the air as it passes through the filter. MERV is a standard used to measure the overall efficiency of a filter. Higher MERV ratings mean fewer dust particles and other airborne contaminants pass through the filter.
MERV ratings are determined by adding particles of varying sizes (1-12) into a controlled testing environment. The particles are added upstream of the test filter and a laser particle counter samples the air before it enters the filter and after it leaves the filter. The two particle counts are compared to calculate the Particle Size Efficiency of the tested filter. Once this is determined, a MERV Parameters chart is used to determine the MERV rating.
MERV ratings range from 1 – 16 and measurements are in microns. Some of the common particles related to MERV ratings are pet dander, insecticide dust, smog, dust, viruses, wood, tobacco smoke, spores, bacteria and pollen.
Some of the most common filters found in residential use only have a merv rating of 1 to 4. These are typically disposable panel type filters and do not do a good job of filtering the air because they will not stop particles smaller than 10 microns.
Merv 5 to 8 rated filters are a better choice and are more commonly found in commercial applications. These filters will collect particles as small as 3 microns and are a good choice for home owners also.
Filters with a merv rating of 9 to 12 are used in commercial and industrial applications and will stop particles in the 1 to 3 micron range. These filters are a great choice for home owners who want the best dust control possible. When using filters with Merv 9 ratings and above it is important to clean or replace them when recommended by the manufacturer because they will have a negative effect on air flow when they become dirty. This can lead to performance problems and decreased operating efficiency.
The most efficient filters have merv ratings of 13 to 16 and will stop particles as small as .3 microns. These filters are used in hospitals and other super clean environments.
We hope you find valuable information in the table below. If you would like to read more about the different furnace filter options and some of the benefits of each, checkout the some of our other pages. Media Air Filters, Pleated Air Filters, HEPA Air Filters, Activated Carbon Air Filters
Electrostatic furnace filters are not listed in the table because they do not have MERV ratings. Arrestance and resistance are terms more commonly used to rate electrostatic filters.
MERV Filter Efficiency Guide |
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| Arrestance | Efficiency | MERV Rating | Types Of Filters | Tested Contaminant |
| 60-80% | < 20% | 1 – 4 | Disposable Panel Filters, Permanent Metal Filters, Fiberglass & Foam Media, Hogshair, Automatic Rolls | Pollen, Spanish Moss, Dust Mites, Sanding & Spray Paint Dust, Textile & Carpet Fibers |
| 80-90% | < 20% | 5 | Pleated Panel Filters, Ring Panel Filters, Synthetic Media | Pudding Mix, Snuff, Powdered Milk |
| 90-95% | 20-30% | 6 | Cube Filters, Self-Supported Filters | Dusting Aids, Cement Dust |
| 90-95% | 25-30% | 6-7 | Pleated Panel Filters | Hair Spray, Fabric Protector |
| 95-98% | 40-50% | 8 | Pleated Panel Filters, Ring Panel Filters, Extended Surface Pocket Filters | Mold Spores |
| 98% | 50-60% | 9-10 | Extended Surface Pocket Filters | Welding Fumes, Nebulizer Drops, Coal Dust, Auto Emissions |
| 99% | 60-70% | 10-11 | Pleated Panel Filters, Extended Surface Pocket Filters, Rigid Cell Filters | Lead Dust, Milled Flour |
| 99% | 80-90% | 12-14 | Pleated MERV 12 Pleated MERV 13 Extended Surface Pocket Filters |
Legionella, Humidifier Dust, Smoke, Copier Toner, Face Powder, Paint Pigments, Insecticide Dust |
| 99% | 90-95% | 14-15 | HEPA-Pure Pleated Extended Surface Pocket Filters, Rigid Cell Filters | Sneeze, Cooking Oil |
| NA | 95% | 16 | Rigid Cell Filters | Bacteria, Tobacco Smoke |
{ 8 comments… read them below or add one }
My ultra efficient Lennox furnace has a Honeywell 16x 25x 4 filter element. MERV 11 . We do not have cats or dogs and our ducts were cleaned just before the Furnace was installed in 2010. Home Depot has Honeywell filters with a different rating system number of 10. Are they similar? (the 4 in dimension is actually 4.375, the others are 1/4 in. less.). Dave
I’n not sure about that Dave. I think Honeywell uses the MERV rating system like most filter manufactureres. As far as I know Filtrete is the only manufacturer that uses their own rating system.
I have a Lennox Conservator III G16 gas furnace no longer produced and live in Central Oregon that has a lot of volcanic dust. Currently I am using a 20 x 25 x 4″ filter with a 8 MERV rating which I change about 3 times per year. My questions are as follows:
!) How high a MERV rated filter can I use to trap more of the dust that ends up in my home?
2) If I increase my MERV rated filters to say 10, do I end up damaging my furnace? What about a MERV 12 rated filter?
3) What about your Nordic Pure MERV 12 filters (and their size?)?
3) Is there a trade-off point and if so, where is it?
Thank you very much for your time and consideration.
1) Unless the manufacturer recommends otherwise, there is no real restriction to what MERV rating you can use. But, it is important to remember that the higher the rating is the greater impact it will have on the operating efficiency of the equipment.
2) There is not a huge difference between a 10 and a 12 rating.
3) A Nordic Pure filter with a MERV 12 rating will basically be the same as any filter of the same rating of equal quality.
4) There is always a trade off when using filters with higher ratings and it is impossible to determine the point at which equipment efficiency is negatively impacted to the point that the gain in filter efficiency is not worth it. This is mostly due to system design and installation. A filter with a high rating will have a much greater impact on a system that is poorly designed and installed than one which is properly designed and installed.
There are many articles in how to section that will provide more information.
Why do furnace manufacturers recommend a very low Merv number (2) in newer furnaces?
I’m not involved in that side of the industry but I think it probably has something to do with the fact that they are making these units so energy efficient. All equipment is designed to operate with a certain minimum air flow. In order for the equipment to operate at the rated efficiencies they require maximum air flows. A MERV 2 filter is not very efficient. Probably one of the cheap fiberglass type.
Also, furnaces have heat exchangers in them which are more sensitive to low air flow. Low air flow in a furnace can make the heat exchanger more susceptible to cracking under certain conditions.
Where to I find the Merv rating on my furnace filter? I currently am using DustStop. Thank you for our assistance,
Sometimes manufacturers stamp the MERV rating somewhere on the frame of the filter but this is more the exception rather than the rule. You should be able to get the information from the supplier or it may be listed on the filter packaging.