Ask An Engineer: What Does MERV Mean?

To an innocent bystander, conversations within an architecture and design and firm can be some of the most convoluted you will ever hear… especially when engineers are involved. Hang around our office long enough, and you’ll encounter more acronyms and elaborate jargon than you’ll know what to do with! This complex language makes complete sense to them while leaving everyone else in the dark.

But, in an effort to stimulate more conversation and create less confusion in the world, we would like to explain what some of this jargon means, what it is used for, and why it is important—starting with MERV.

Merv isn’t just an ancient city along the historical Silk Road in what is now known as Turkmenistan. Minimum Efficiency Reporting Values, or MERVs, are the measure of an air filter’s ability to capture large particles found in the air, such as dirt, dust, allergens and debris, and prevent them from entering your vents. The scale rates different types of air filters on a scale from 1-16, with one being the lowest possible MERV ranking, indicating less than 20% efficiency on even the largest particles. In comparison, a rank of 16 means the filter is greater than 75% effective against even the smallest of air particles. These highly effective filters can trap debris in the air as small as 0.3 microns. For reference, the average dust particle found in the air is anywhere from 1-100 microns, while some viruses transferred through the air are as small as .01 microns.

Some of the most common filters found in residential use only have a MERV rating of 1-4. These are typically disposable panel-type filters and will not stop particles smaller than 10 microns. This is acceptable for homes, but not for commercial or industrial use.

MERV 5-8-rated filters are a more common and better choice in commercial applications. These filters will collect particles as small as three microns. Filters with a MERV rating of 9-12 will stop particles between 1-3 microns. When it comes to schools, specifically, the Ohio School Design Manual requires education buildings to have air filters with a MERV of at least 13. This is why SHP almost exclusively uses filters with a rating of 13-16.

Any of these filters are a great choice when indoor air quality is of the highest importance. Like any part of your HVAC system, air filters of any kind must be changed regularly and checked often.