What is a MERV rating?

MERV stands for Minimum Efficiency Reporting Value and is a measurement scale developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (known as ASHRAE) as a way of reporting the effectiveness of air filters. This is particularly relevant in the field of improving indoor air quality.

The MERV rating scale is designed to demonstrate the worst case performance of a filter in filtering particles in the range of <0.3 to 10 micrometers. As the MERV level gets higher, it shows a corresponding greater percentage of particles filtered on each pass, and therefore a better air filtration level. In terms of improving indoor air quality, understanding the MERV rating of any air filtration system that is being considered is an important aspect.

A table designed to show MERV ratings, airborne contaminant particulate sizes, how to measure the effectiveness of any air purification system and the typical application of MERV filtration systems is shown below.

Did you know the i-air pro has a MERV rating of 19 filtering out viruses?