Many people get a little confused when deciding what filters to buy and the things to look out for in selecting the one that suits them best. There are many places online that sell air and furnace filters of various specifications and some go as far as making sure you have your filters delivered to your home as an extra benefit to you, but that should not be the major thing to look out for. After all what’s the use of having the luxury of getting you filters delivered to you if you don’t take the time to choose the one that suits your needs the best.
An important factor to consider when deciding what filter to buy for your home is what is known as the MERV rating. MERV stands for Minimum Efficiency Reporting Value, and it is basically a way to tell the size of particles the filter is designed to catch. The measurement scale was designed by the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) in 1987 to rate how effective an air filter is. It was introduced to improve the "precision and accuracy of air-cleaner ratings", and further helps to reduce cost and increase energy efficiency and overall health.
The MERV rating is on a scale of 1 to 20, with 1 being the lowest and 20 being the highest in cost and efficiency. The ASHRAE recommends a filter with a minimum MERV rating of 6, while the U.S. Department of energy advises a minimum rating of 13 but most residential filters have a rating from 4 to 12. And on average a 7 or 8 rated filter is a good balance between cost and air filtration efficiency, as they are able to capture approximately 85 percent of particles 3.0 to 10.0 pm particle size. Examples of particles within this size range are mould spores, cement dust, pudding mix and hair spray. They also make easy work of catching larger particles 10.0 pm particle size like pollen, dust mites, sanding dust and textile and carpet fibres.
The two variables used to determine the efficiency and rating of a filter are Arrestance and Dust Spot Efficiency. Arrestance is the term used to describe the filter’s ability to remove injected standard dust from the test air and is calculated as a percentage relationship on a weight basis. The dust spot efficiency is described as a measure of the ability of a filter to remove atmospheric dust from air. This is also expressed as a percentage.
|MERV RATING CHART|
|Standard 52.5 Minimum Efficiency Reporting Value||Dust Spot Efficiency||Arrestance||Typical Controlled Containment||Typical Applications and Limitations||Typical Air Filter/Cleaner Type|
|20||n/a||n/a||< 0.30 pm particle size||Clean rooms||>99.999% eff. On 10-20 pm Particles|
|19||n/a||n/a||Virus (unattached)||Radioactive Materials||Particles|
|18||n/a||n/a||Carbon Dust||Pharmaceutical Man.||Particulates|
|17||n/a||n/a||All Combustion smoke||Carcinogenetic Materials||>99.97% eff. On 30 pm Particles|
|16||n/a||n/a||0.3-1.0 pm Particle Size||General Surgery||
|15||> 95%||n/a||All Bacteria||Hospital Inpatient Care|
|14||90% - 95%||> 98%||Most Tobacco Smoke||Smoking Lounges|
|13||89% - 90%||> 98%||Droplet Nuclei (Sneeze)||Superior Commercial Buildings|
|12||70% - 75%||> 95%||1.0-3.0 pm Particle Size Legionella||Superior Residentia||
|11||60% - 65%||> 95%||Humidifier Dust Lead Dust||Better Commercial Buildings|
|10||50% - 55%||> 95%||Milled Flour Auto Emissions||Hospital Laboratories|
|9||40% - 45%||> 90%||Welding Fumes|
|8||30% - 35%||> 90%||3.0-10.0 pm Particle Size||Commercial Buildings||
|7||25% - 30%||> 90%||Mould Spores Hair Spray||Better Residential|
|6||< 20%||85% - 90%||Fabric Protector Dusting Aids||Industrial Workplace|
|5||< 20%||85% - 90%||Cement Dust Pudding Mix||Paint Booth Inlet|
|4||< 20%||75% - 80%||Minimal Filtration||Paint Booth Inlet|
|3||< 20%||70% - 75%||Dust Mites Sanding Dust||Residential|
|2||< 20%||65% - 70%||Spray Paint Dust|
|1||< 20%||< 65%||Textile Fibres Carpet Fibres||Window A/C Units|
With the above information, it should be relatively easy to make the best decision on what filter to buy, now once you have that, you can think about buying from a company that provides the extra service of having your chosen.