What is a MERV Rating?
WHAT IS MERV?
Minimum Efficiency Reporting Value, commonly known as MERV Rating is a measurement scale designed in 1987 by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) to rate the effectiveness of air filters.
The scale is designed to represent the worst case performance of a filter when dealing with particles in the range of 0.3 to 10 microns. The MERV rating is from 1 to 16. Higher MERV ratings correspond to a greater percentage of particles captured on each pass.
This is now an international industry standard set up by the committee that oversees the filter industry. This standard is used for determining the filters ability to capture and hold dirt and dust in specific size ranges. Some filter manufacturers such as 3M use their own rating system, which is not approved as an industry standard.
DOES A HIGHER MERV RATING = A BETTER FILTER?
Generally, yes. A filter with a higher MERV rating will be able to remove smaller particles from the air passing through it. This means the air you breathe will be cleaner.
MERV RATINGS FOR COMMON FILTERS:
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. NOTE: Filters in this range usually are not advertised with any specific MERV rating.
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 homeowners who want the best dust control possible. When using filters in this group it is important to change them on a regular schedule because if they become heavily loaded with dust they can have a negative impact on equipment performance.
MERV RATING MATRIX:
|MERV Rating||Average Particle Size Efficiency in Microns|
|1-4||3.0-10.0 - less then 20% Efficient|
|6||3.0-10.0 - 35 - 49% Efficient|
|8||3.0-10.0 - 70 - 84.9% Effecient|
|10||3.0-10.0 - 85% or greater / 1.0 - 3.0 - 50 -64% Efficient|
|12||3.0-10.0 - 90% or greater / 1.0 - 3.0 - 80 - 89.9% Efficient|
|14||3.0-10.0 - 90% or greater / 1.0 - 3.0 - 90% or greater|
|16||3.0-10.0 - 95% or greater / 1.0 - 3.0 - 95% or greater|
A human hair is 20-40 microns in width.