- Dennis Griffin
Understanding MERV Filter Ratings
MERV Rating (Minimum Efficiency Reporting Value) is a standard set by ANSI/ASHRAE that is used to measure the overall efficiency of an air filter. Higher MERV ratings are assigned to filters capturing the greatest percentage of airborne particles and contaminants. Filters with MERV ratings of 1 to 16 are capable of filtering particles ranging from 0.3 to 10 microns. Higher MERV ratings of 17-20 are assigned to HEPA and ULPA filters capable of trapping particles smaller than 0.3 microns.
Since 2020 ASHRAE has recommended upgrading filtration to MERV 13 or higher to mitigate the spread of Covid-19 as well as other viruses and bacteria. But many commercial HVAC systems aren’t designed to accommodate high-MERV filters, which can increase pressure drop and reduce airflow. PJM can help clients determine the highest MERV rating possible for their existing system, and in some cases can make system modifications to allow higher-efficiency filters to be used or help relieve the negative effects of higher-MERV filtration.
MERV 1-4 – Residential and light commercial filters with minimal filtering ability. Can trap particles 10 microns and above.
MERV 5-8 – A better choice for residential use, commonly used in commercial settings and industrial workplaces. Capable of capturing particles as small as 3 microns (mold spores, dust mite debris, pet dander).
MERV 9-12 – Capable of filtering particles of 1 to 3 microns such as Legionella, humidifier dust, lead dust. The best option for residential, mostly used in commercial and industrial applications.
MERV 13-16 – Preferred for most hospital and healthcare applications, superior choice for commercial buildings. A MERV 16 filter captures 95-99% of particles spanning the full test range including bacteria and tobacco smoke.
MERV 17-20 – Used in pharmaceutical, electronics manufacturing, clean rooms, hazardous materials and nuclear applications, these filters are capable of filtering 99.97-99.9999% of particles including viruses, radon, and carbon dust. Impractical for typical HVAC systems.