Air Filters And MERV Ratings: What You Need To Know


Air filters come in several different types, and each type has varying degrees of efficiency.

Filters have a minimum efficiency reporting value, or MERV rating, which measures their efficiency on a scale from 1 to 20. MERV ratings give you an easy way to compare filters, but you still need to know what the various MERV ratings mean if you want to get air filters that suit your needs.


MERV Ratings

The minimum MERV rating for devices such as window air conditioners is 4. A rating of 4 means the filter can catch particles less than 10 microns in size, which includes things like pollen and dust mites. These filters provide minimum filtration, and are more for protecting the HVAC equipment itself rather than cleaning your home’s air. Air filters that are rated in the 6-12 range are medium-efficiency filters. MERV ratings from 6-8 can catch particles 3-10 microns in size, which include mold spores and pet dander. In the 9-12 range, filters can catch some bacteria. Filters in the 9-12 range are considered superior for residential applications.


HEPA Filters

True high-efficiency particulate air (HEPA) filters are the most efficient, having a MERV rating from 17-20. HEPA filters can catch some viruses and even smoke particles. They are often used in environments such as pharmaceutical manufacturing. They can be attached to some furnaces and air conditioners, but not all residential HVAC equipment has the airflow capacity necessary to accomodate a HEPA filter. If you’re considering a HEPA filter, you should consult your HVAC equipment’s documentation or talk with an HVAC specialist like Crawford Services to make sure that your equipment can properly recieve the desired air filtration. If your system is not compatible for a HEPA Filter, then we can recommend a standard filter with MERV ratings of 13-16, which are able to catch all bacteria and most smoke particulate sand pet odors . If you would like to consult a professional regarding air filtration for your heating and cooling equipment, contact Crawford Services for advice on your air quality needs. We’ll be happy to help.