What Are Merv Ratings For Air Filters?
MERV stands for minimum efficiency reporting value is a scale used to measure the efficiency of the air filters. MERV ratings were originated by American Society of Heating, Refrigerating and Air conditioning (ASHRAE) in the year 1987.
Higher the MERV rating smaller the holes in the filters and higher will be the efficiency of your air conditioning system. Higher the ratings smaller the particles can be captured inside the filter.
It is necessary to select the filters of proper MERV ratings for your air conditioners. Higher the MERV rating smaller the holes of the filters and lesser the air will reach inside the system. If the pores to small than your system can handle than it can result in various issues.
If less amount of air reaches inside the system it will take more time for the system to cool, can result in poor quality of air inside your home and can cause damage to the fan of your furnace or even your air conditioning system. So it is necessary to select the air conditioning of proper size.
Filters with higher MERV ratings are required to be change more frequently as they are can restrict the flow of air very easily. MERV ratings for houses and buildings are mostly from 1 to 16 however it can also reach up to 20 in some cases.
This is how MERV ratings do work
• MERV 1 to 4 less than 20% of large particles of size 3-10 microns is caught. These filters are mostly used to protect the equipments are mostly used in industrial places and residential applications.
• Ratings between 205 to 70% of large particles of size 3-10 microns are captured. These are used in devices where it is more important to protect individuals from the pollutants.
• MERV ratings from 8-10 nearly 85% of large particles and 50% of small particles of size 1 to 3 microns. These are used for superior residential buildings.
• 11- 16 higher than 90% of large particles and70-90% of small particles. These are most commonly used filters in heat pumps and air conditioner in hospitals.
• If ratings are from 17-20 the smallest particles of less than 0.3 microns are captured. Mostly used in Clean rooms and pharmaceutical manufacturing.
| MERV RATING CHART |
| Standard 52.5 Minimum Efficiency Reporting Value |
Dust Spot Efficiency |
Arrestance |
Typical Controlled Containment |
Typical Applications and Limitations |
Typical Air Filter/Cleaner Type |
| 20 |
n/a |
n/a |
< 0.30 pm particle size |
Clean rooms |
>99.999% eff. On 10-20 pm Particles |
| 19 |
n/a |
n/a |
Virus (unattached) |
Radioactive Materials |
Particles |
| 18 |
n/a |
n/a |
Carbon Dust |
Pharmaceutical Man. |
Particulates |
| 17 |
n/a |
n/a |
All Combustion smoke |
Carcinogenetic Materials |
>99.97% eff. On 30 pm Particles
Bag filter – Non supported micro fine fibre glass or synthetic media, 12-36 in. deep, 6-12 pockets |
| 16 |
n/a |
n/a |
0.3-1.0 pm Particle Size |
General Surgery |
Bag filter – Non supported micro fine fibre glass or synthetic media, 12-36 in. deep, 6-12 pockets |
| 15 |
> 95% |
n/a |
All Bacteria |
Hospital Inpatient Care |
| 14 |
90% - 95% |
> 98% |
Most Tobacco Smoke |
Smoking Lunges |
Box filter - Rigid Style Cartridge Filters 6 to 12" deep may use lofted or paper media |
| 13 |
89% - 90% |
> 98% |
Prop let Nuclei (Sneeze) |
Superior Commercial Buildings |
| 12 |
70% - 75% |
> 95% |
1.0-3.0 pm Particle Size Legionella |
Superior Residential |
Bag filter - Not supported micro fine fibre glass or synthetic media, 12-36 in. deep, 6-12 pockets Box filter - Rigid Style Cartridge Filters 6 to 12" deep may use lofted or paper media |
| 11 |
60% - 65% |
> 95% |
Humidifier Dust Lead Dust |
Better Commercial Buildings |
| 10 |
50% - 55% |
> 95% |
Milled Flour Auto Emissions |
Hospital Laboratories |
| 9 |
40% - 45% |
> 90% |
Welding Fumes |
| 8 |
30% - 35% |
> 90% |
3.0-10.0 pm Particle Size |
Commercial Buildings |
Pleated Filters - Disposable, extended surface area, thick with cotton-polyester blend media, cardboard frame Cartridge Filters - Grated density viscous coated cube or pocket filters, synthetic media Throwaway - Disposable synthetic panel liner |
| 7 |
25% - 30% |
> 90% |
Mould Spores Hair Spray |
Better Residential |
| 6 |
< 20% |
85% - 90% |
Fabric Protector Dusting Aids |
Industrial Workplace |
| 5 |
< 20% |
85% - 90% |
Cement Dust Pudding Mix |
Paint Booth Inlet |
| 4 |
< 20% |
75% - 80% |
> 10.0 pm Particle Size Pollen |
Minimal Filtration |
Throwaway - Disposable synthetic panel liner Washable - Aluminium Mesh Electrostatic - Self-charging woven panel filter |
| 3 |
< 20% |
70% - 75% |
Dust Mites Sanding Dust |
Residential |
| 2 |
< 20% |
65% - 70% |
Spray Paint Dust |
|
| 1 |
< 20% |
< 65% |
Textile Fibbers Carpet Fibbers |
Window A/C Units |
Limitations of MERV ratings
MERV ratings are given on the basis of capacity of air filters to capture dust particles. But only dust particles are not responsible for air pollution. Air pollution is also caused due to various hazardous gasses which will easily pass through these filters and reach our house.
MERV ratings are applicable on only big air filters which are used to filters the air of entire building or complex these ratings are not applicable on small air filters.