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Understanding MERV Ratings for Air Filters
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, washable hog’s hair or washable foam 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.
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.
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MERV Filter Efficiency Guide |
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 Panel Filters, Extended Surface Pocket Filters, Rigid Cell Filters
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Legionella, Humidifier Dust, Smoke, Copier Toner, Rigid Cell Filters, 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 |
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