MERV stands for Minimum Efficiency Reporting Values and is an industry-created
standard that evaluates the efficiency of air filters. The MERV rating of
any particular air filter ranges on a scale of 1 to 16, with a filter rating
1 being the least efficient and a filter rating 16 being the most efficient.
While it is important for the quality of the air in your home to choose the
most efficient filter possible, it is not always as simple as buying a filter
with the highest MERV rating. Because the pores allowing for air flow in
a highly-rated MERV filter are very small, the filter creates more resistance
against air flow and may put too much pressure on the fan of your furnace
or air conditioning unit. It’s important to choose an air filter with
the highest MERV rating that your particular unit will allow for maximum
air flow. Information about specific MERV ratings and recommendations for
your furnace will generally be included with the documentation that came
with your system.
We recommend choosing an air filter with a MERV rating between 8 and 11 for
most residential furnace and AC units in order to adequately remove airborne
contaminants. If your system can handle a filter with a higher MERV rating,
you may wish to use a filter with a rating of 12 or 13 for even greater contaminant
removal. However, it’s important to remember that filters with a higher
MERV rating must be replaced at least every three months to avoid restricted
air flow and negative effects on your furnace’s performance.
Changing your filters regularly and using the most efficient filter possible
for your furnace is the best way to control the air quality in your home
and maximize the lifetime of your heating and cooling unit. A little research
into MERV ratings will certainly pay off – in better health and improved
Lint and dust particles are typically present in any indoor environment and can range in size from .3 microns to 100 microns. Household dust is made up of a variety of ingredients including dead skin cells, small insect and plant parts, tiny particles of dirt, and loose fibers from fabric (commonly known as lint). Like any allergen, too much exposure to dust and lint can kick the immune system into gear, causing allergic reactions like sneezing, runny nose, and watery eyes.
Removing lint and dust particles both prevents dust build-up on the fan and coils of your furnace unit and stops these potential allergens from being released into the air. Nearly any air filter with a MERV rating of 8 or higher will efficiently remove these contaminants from the household air.
Dust mites are tiny insects that are closely related to spiders and ticks. They feed on the dead skin cells that flake off our bodies and are present wherever humans live. Although the dust mite itself is typically larger than 10 microns, the debris a mite leaves behind (shed skin, feces, and other excretions) can be anywhere in size from .3 microns to 10 microns.
Dust mite debris is second only to pollen as the most common cause of allergic reactions in humans. Like any allergen, too much exposure to dust mite debris can kick the immune system into gear, causing allergic reactions like sneezing, runny nose, and watery eyes. Nearly any air filter with a MERV rating of 8 or higher will efficiently remove these contaminants from the household air.
Pollen is a tiny particle created by flowers as a part of the reproduction process. It is carried by the wind from flower to flower and is often present in both indoor and outdoor air. Pollen is the most likely of any other airborne contaminant to cause an allergic reaction, and once it finds its way into the body it can cause symptoms like sneezing, runny nose, and water eyes.
Pollen particles are relatively large (ranging in size from 10 to 100 microns) and can be efficiently removed by any air filter with a MERV rating of 8 or higher.
Mold is a tiny organism that belongs to the fungi kingdom, meaning it is not classified as either plant or animal. Mold is commonly present in any household because it likes to feed on things like wood beams, ceiling tiles, wallpaper, paint, carpet, and insulation. When mold reproduces, it creates a number of tiny mold spores (approximately 3 to 40 microns in size) that function like seeds. If mold is disturbed during the reproduction process, it can release these spores into the household air.
Like any allergen, too much exposure to mold spores can kick the immune system into gear, causing allergic reactions like sneezing, runny nose, and watery eyes. Nearly any air filter with a MERV rating of 8 or higher will efficiently remove these contaminants from the household air.
Pet dander refers to the tiny flakes of skin that animals naturally shed as their skin cells die and flake off. For most people who suffer from pet allergies, it is the dander and not the hair of the animal that causes an allergic reaction. Pet dander is often in the air and can stay suspended in the household air for many months after an animal has been in the home.
Particles of pet dander are typically 10 to 100 microns in size and can cause a range of allergic reactions including sneezing, runny nose, watery eyes, coughing, wheezing, and even asthma attacks. Nearly any air filter with a MERV rating of 8 or higher will efficiently remove these contaminants from the household air.
Auto emissions are fumes that are released into the air as a part of the combustion process in a gasoline engine. The fumes are made up of a number of different gases including unburned hydrogen carbon, carbon monoxide, nitrogen oxide, and carbon dioxide. While they are more commonly a concern in commercial or industrial buildings, auto emissions can enter the household air through vents that suck air from the outside and the opening of household doors. Breathing in too many of these fumes can irritate and/or damage the lungs.
Particles containing auto emission fumes typically range from 1 to 3 microns in size and can be efficiently removed by an air filter with a MERV rating of 9 or higher.
Smoke can enter the household air from a variety of sources including cigarettes, cigars, wood-burning fireplaces, and industrial activities outside the home. In addition to a number of different carcinogenic gases and chemicals, smoke can also contain tiny particles of wood tars, ashes, and soot. Too much exposure to smoke can cause the typical allergic reactions of sneezing, runny nose, and water eyes, as well as burning eyes, bronchitis, and asthma attacks.
Because particles of smoke are quite small (typically 0.3 to 1.0 microns in size), an air filter with a MERV rating of 11 or higher is required to efficiently remove them.
Tobacco smoke is typically only present in the household air if you or someone else in the house smokes. It contains many different carcinogenic chemicals and gases, and too much exposure can cause the typical allergic reactions of sneezing, runny nose, and water eyes, as well as burning eyes, bronchitis, asthma attacks, and some types of cancer.
The particles of tobacco smoke that stay in the air and cause odors are typically less than 1 micron in size and can only be removed by an air filter with a MERV rating of at least 13.
Bacteria are tiny microorganisms that are present everywhere. They are in everything we touch and breathe, and the bacteria found within our bodies actually outnumber our own cells. There are a variety of good bacteria that help us to digest food and fight off sickness, but there are also some types of harmful bacteria that can cause illnesses like pneumonia, strep throat, and a number of infections.
Bacteria particles in the air are very small (ranging in size from 0.3 to 1.0 microns) and require a filter with a MERV rating of at least 13 to be efficiently removed. However, if you are concerned about bacteria in your household air, the best method for removal and treatment is a HEPA air filtration unit.