What are the benefits of Air Filteration?

Adding a high quality air filter to your household air conditioner offers many benefits besides the obvious benefit of healthier, cleaner air.  A high quality air filter helps remove debris, such as lint and dust from the heating/cooling coils of your A/C unit.  When you add a high quality filter, it helps your A/C unit last longer and have fewer expensive maintence calls.  Also, a high quality air filter removes tiny particles that may cause electrical equipment to malfunction, such as your computer or expensive sound equipment.

Some of the many other benefits of air filteration include the general cleanliness of your home, reduction in the household/building maintenence due to dust build-up, reduction of fire hazards caused by debris build-up in your ductwork and/or air handler, and the reduction of airborne bacteria, mold, and allergens.

The organization that designs standards for testing air filteration equipment is named ASHRAE.  ASHRAE stands for the American Society of Heating, Refrigerating, and Air-Conditioning Engineers.  It is a large international organization dedicated to the advancement of these technologies.  The air filtration industry generally uses the ASHRAE 52.2 and ASHRAE 52.1 efficiency tests to test residential and commercial panel type air filters, such as, fiberglass, polyester, and pleated type. 

ASHRAE 52.2 focuses on testing Particle Size Efficiency (PSE).  The test itself is entitled, "Method of Testing General Ventilation Air Cleaning Devices for Removal Efficiency by Partical Size."  This test measures the ability of the air filter to remove certain sized particles from the air and resistance.  A simple explanation of the test is as follows.  When the test is performed, an aerosol is blown into a test filter.  The test uses 12 different sized particles that start at the size of 0.3 micrometers (micrometer = 1 millionth of a meter) and ends at 10 micrometers.  Particle sizes are raised in size slowly over the period of the test.  A particle counter measures the percentage of particles the filter removes from the air.  The air resistance test measures how much the filter restricts the air flow in your air conditioning system. 

ASHRAE 52.1 is an older efficiency test that focuses on arrestance value, dust spot testing, and dust holding capacity.  ASHRAE 52.1 is named "Gravimetric and Dust Spot Procedures for Testing Air Cleaning Devices Used in General Ventilation for Removing Particulate Matter."  The arrestance value compares the percentage of weight of dust the filter removes against the total weight of dust that is fed into the filter.  Instead of testing various sizes of particles separately, this test uses a variety of different sized particles all at once.  So it is a less accurate test for determining how fine of a particle the filter can remove.  The dust spot test measures how efficiently the filter can remove the staining portion of dust particles by comparing discoloration.  In the ASHRAE 52.1 test, when the term efficiency is used, they are referring to the dust spot test.  And finally, in the 52.1 test, the dust holding capacity will be measured.  Dust holding capacity measures the weight of dust in grams that the filter is capable of holding before reaching too much of a drop in air pressure.  After the filter becomes dirty, the air resistance is measured.  The air resistance of the dirty filter will help determine the dust holding capacity.  ASHRAE 52.1 is an older test that is viewed as somewhat less reliable for measuring filter efficiency.  However, it is still a commonly used test and is a useful tool for comparing different filters.

After these tests are performed, the filter is assigned a MERV rating, which is a Minimum Efficiency Reporting Value.  Filters can have a MERV rating as low as 1 and as high as 20.  Though, you most likely will never see a product labeled lower than MERV-8.  The MERV rating is assigned according to the filter's capabilities after reviewing the 52.1 and 52.2 tests.  This rating shows you the LEAST possible efficiency you can expect from the filter.