What is a MERV Rating

Understanding MERV Ratings

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 this information helpful. If you would like to read more about
the different furnace filter options and some of the benefits of each, checkout our
other pages. Media Air Filters, Pleated Air Filters, HEPA Air Filters, Activated
Carbon Air Filters