A filter with a MERV rating of around 10 to 12 is enough to remove most allergy-causing particles from your home's air. Most air filters that are capable of eliminating common allergens have the word “allergy” or “allergen” on their packaging. This indicates that you are on the right track. The MERV rating you choose between 7 and 13 depends on the level of filtration you need.
If your family has allergies or asthma, a higher MERV score will be good for you. If your family doesn't have any shortness of breath, a lower filter, such as a 7, will save you some money on your energy bill. Simply put, these filters will have the least restriction to air flow and will trap the lowest volume of particles. This all sounds great, and it also makes it look like the stronger the filter, the better it will be for your home, but it's not like that.
The chart also uses percentages based on the chances of an air filter capturing dust particles based on micron size. However, against these warnings there is a mountain of owner testimonies that MERV 11, 12 and even 13 filters have worked well in their systems for years. But to go into more detail about the two, consider that MERV 11 filters trap 65 to 79 percent of the average particles 1.0 to 3.0 microns in size, with an average particle size efficiency of 85 percent or better. In addition, a MERV 12 filter that is only 1 (one inch) thick is likely to be more restrictive than a 4 (four inch) thick MERV 12 filter.
A filter with a MERV rating between 1 and 6 can remove particles between 0.3 and 10 microns with an efficiency of 20%. While the air filter is designed to control the amount of unwanted air particles entering your home, your filter's MERV rating is meant to show you which filter is best for your home. If you can't find Nordic Pure in your size, or if you prefer to buy and buy a new filter from a store immediately, Honeywell's FPR 9 filters and Filtrete MPR 1500 filters are similar and widely available in retail stores. You should also remember to replace the filter every month, three months, six months or year, depending on the filter.