The acronym MERV stands for "Minimum Efficiency Reporting Value." MERV ratings are used to rate the ability of an air cleaner 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. The MERV scale ranges from 1 to 16, and measures a filter's ability to remove particles from .3 to 10 microns in size. To give you an idea of the scale of a micron, 100 microns is about the thickness of a piece of paper or a human hair. Filters with higher ratings not only remove more particles from the air, they also remove smaller particles.
MERV ratings are determined by adding particles of varying sizes 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.
See the MERV Rating Chart below for more information about the difference in performance between filters with different MERV ratings.
|
MERV Rating |
Dust Spot Efficiency* |
Typical Controlled Contaminant |
Applications |
Air Filter Types |
|
1 |
<20% |
>10 micron Particle Size
Pollen, Dust Mites, Sanding Dust, Textile Fibers, Carpet Fibers |
Minimal Filtration
Residential
Window A/C Units |
Throwaway – Disposable fiberglass or synthetic
Washable – Aluminum
Electrostatic – Self Charging |
|
2 |
<20% | |||
|
3 |
<20% | |||
|
4 |
<20% | |||
|
5 |
<20% |
3-10 micron Particle Size
Mold Spores, Hair Spray, Fabric Protector, Dusting Aids, Cement Dust |
Commercial Buildings
Better Residential
Industrial Workplace
Paint Booth Inlet |
Pleated – Disposable, extended surface area
Throwaway – Disposable synthetic panel |
|
6 |
<20% | |||
|
7 |
25-30% | |||
|
8 |
30-35% | |||
|
9 |
40-45% |
1-3 micron Particle Size
Legionella, Humidifier Dust, Lead Dust, Auto Emissions, Welding fumes |
Better Commercial
Superior Residential
Hospital Laboratories
Welding Booth Inlet |
Bag Filter - synthetic media, typically 6”-36” deep
Box Filter – cartridge, typically 4” deep |
|
10 |
50-55% | |||
|
11 |
60-65% | |||
|
12 |
70-75% | |||
|
13 |
89-90% |
.3-1 micron Particle Size
All Bacteria, Most Tobacco Smoke, Proplet Nuceli (Sneeze) |
Superior Commercial
General Surgery
Hospital Rooms
Smoking Lounge |
Bag Filter - synthetic media, typically 6”-36” deep
Box Filter – cartridge, typically 4” deep |
|
14 |
90-95% | |||
|
15 |
>95% | |||
|
16 |
>95% |
* Dust spot efficiency measures a filter's ability to remove large particles, those that tend to soil building interiors.