MERV Rating Chart
A MERV rating chart shows a numerical value. The range is from 1 (lowest efficiency) to 20 (highest efficiency). MERV stands for Minimum Efficiency Reporting Value. This is an industry standard rating system. Use this rating system compare filters made by different manufacturers. This rating system reports how well the filter captures and holds dust. The chart below shows the MERV ratings. It shows particle size ranges. It also shows air filter efficiency levels. Efficiency is measured by the percentage of particles captured. In January 2009 ASHRAE stopped recognizing MERV 17 -20 values. These values are shown to reflect the common vernacular used by many players in the filtration industry
This Video Explains the MERV Filter Rating Chart
Higher = More Filtration in the MERV Filter Rating Chart
Generally, the higher the MERV (M), you get better filter performance. M values 1 through 4 are designed to remove large particles. These filters are used primarily to protect equipment. They are used in light industrial and residential applications. Their average efficiency from 3 to 10 micron is less than 20. The Average arrestance is used to determine MERV 1 through 4. A lint trap in a dryer is about M 2
Filters with a (M) value 5 through 8 remove finer dust particles. These air filters are used to protect people or products from airborne contaminants. These particles could hurt health and productivity.
MERV 9 through 12 filters are good filters for general home use. They remove the bulk of dust we see in homes and offices. They generally allow enough air to flow through a furnace filter to allow the blower to stay cool. Their cost is often moderate and are within many budgets.
A M rating of 13 through 16 are higher quality filters. They require special blowers to pull the air through them. These filters should not be used in home HVAC or furnace systems. They are usually reserved for superior commercial applications.
HEPA and ULPA filters are represented in the 17 through 20 ratings. ASHRAE no longer recognizes MERV 17-20 values. This level of filtration does fall into the MERV system but they are shown here to add continuity to the overall filter picture. These filters remove at least 99.97% of dust particle and are capable of removing viruses and radioactive material.
LakeAir replacement filters use 4 different MERV rated filters. Pre filters are rated MERV 2. The furnace filter frames use a M 10 rated level air filter. Our Media Air purifiers use MERV 11 filters. LakeAir Commercial units have the ability to incorporate a MERV 14 High capacity media filter
At LakeAir, we recommend MERV 10 filters as our “good” air filter. These filters do a good job at removing harmful indoor air pollution. They offer good airflow. M 10 filters are easy on air blowers and fans.
We recommend MERV 11 filters as our “better” air filter. These air filters are great for people with pets. They remove pet dander and most allergy causing air particles. These include mold, smoke and pollen. We do not recommend M 12 or higher 13 filters. They may negatively affect certain HVAC systems. These filters can cause restricted airflow. The blowers in HVAC units rely on a good air supply to keep them cool.
The High Capacity MERV 14 Media filter (HC-14) provides a large volume of dust capacity. This 4 inch filter has over 60 square feet of synthetic dirt grabbing fibers. It is 75% efficient on particles 0.3 -1.0 microns, 85% efficient on particles 1-3 microns and 95% efficient on particle larger than 3 microns. The filter has a Galvanized steel frame, the filter dimensions are 20″ x 19.75″ x 3.75″. The Back pressure from this filter is 0.22 WG.
Our HEPA filter systems are our “best” media air filters they remove 99.97% of all impurities. They are available for the home and business. They will not hook up to your furnace or HVAC system.
Electrostatic air filtration is not easily compared to media filters. Its and apples and oranges kind of thing. In some ways they are better than all media filters in others they have drawbacks. The (M) rating is 16 or above and they are washable.
LakeAir Electrostatic Air Filters work as well as a MERV 16 air filter. They are washable. They never need to be replaced. The Maxum electrostatic is a great air purifier for your home. If you have more questions about the right air filter or air purifier, call our customer service number 800-558-9436. We will help you understand your best air filtration options.
Every air purification system should have an activated carbon filter. Activated carbon filters remove VOCs and odors. VOCs and odors are not covered by ASHRAE tests. So, whatever air filtration you choose, be sure it includes a carbon filter.
Merv Rating Test Procedure
ASHRAE developed the MERV air filter efficiency rating system. ASHRAE stands for the American Society of Heating, Refrigerating, and Air-Conditioning Engineers. The rating system is called ASHRAE Standard 52.2-2007. This method tests Air-Cleaning Devices for dust removal efficiency. The test is based on particle size. Standard 52.2 establishes a testing protocol. It ensures reliable and consistent testing of air filter performance. The performance is based on particles that are 0.3-10 micron in diameter. This Standard is what led to the creation of the minimum efficiency reporting value, or MERV. This guideline determines a filters performance by particle size. The filter is assigned a value based on the test. This value is used at the filters lowest efficiency. This is usually when the filter is new.
The test begins with a clean filter. The test is made of six cycles. During each cycle a predetermined amount of dust particles is released into the airstream. These dust particles fall into three size groups.
The amount of E1, E2 and E3 dust particles that are captured and missed is calculated. The process is repeated 6 times. The poorest performance of the filter on all three particles sizes during each of the 6 cycles is used to determine the filters MERV rating. The poorest performance is used. This is how they get the name MERV (MINIMUM Efficiency Rating Value).
Arrestance is a term often used in describing filter performance. Arrestance is a measure of the ability of an air filtration device to dust from the air. The E3 arrestance describes how well an air filter removes larger particles – such as dirt, lint, hair, and dust. E2 arrestance is for the middle size particles. These particles are 1-3 microns. Welding fumes and milled flour are this size. E1 particle ar .3 to 1 micron and they include bacteria and tobacco smoke.
The Chart below shows the scale used to evaluate each of the 6 test cycles. While it is not important to fully understand the comparison chart, it is good to familiarize yourself with it. The informed consumer is a powerful force in the marketplace.
The Test Results
The test results are then used to give a filter its MERV rating.
The Velocity (speed) of the air flow is tested at 1 of 7 different speeds. The speed at which the test was done is noted in the test results. The possible air speeds used for testing is as follows:
118 FPM (0.60 m/s)
246 FPM (1.25 m/s)
295 FPM (1.50 m/s)
374 FPM (1.90 m/s)
492 FPM (2.50 m/s)
630 FPM (3.20 m/s)
748 FPM (3.80 m/s)
The resulting rating is theen given to each filter. The chart below shows a detailed description for each MERV rating 1 through 16. MERV Ratings 17-20 reflect values that are used in the rating of HEPA and ULPA filters.