What Is A MERV Rating?

The MERV rating scale is a way of measuring and reporting the effectiveness of air filtration or indoor air quality management systems.

The acronym 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).

The MERV rating scale is designed to demonstrate the worst case performance of a filter in filtering airborne particles in the range of <0.3 to 10 micrometers. As the MERV level gets higher, it shows a corresponding greater percentage of particles removed from the air on each pass, and therefore a better air filtration level.

In terms of improving indoor air quality, it's important to understand the MERV rating of any air filtration system you're considering.

Simply put, the higher the MERV rating of a filter, the better your indoor air quality is likely to be.

The table below shows MERV ratings, airborne contaminant particulate sizes, how to measure the effectiveness of any air purification system and the typical application of MERV filtration systems.


MERV filtration levels of an air purification device or system are not the only factor to consider in improving indoor air quality.

Indoor air quality, or IAQ as it is commonly abbreviated, is made up of multiple factors. These include VOC’s (Volatile Organic Compounds), carbon dioxide levels, PM2.5 and PM10 airborne particulates, airborne bacteria and microbes as well as other potentially airborne matter.

The best air filtration devices use more than just filtration (ie high level MERV rated filters) to generate the highest levels of output air quality. This could include UV-A and UV-C technology for bacterial reduction, and/or photocatalytic oxidation (known as PCO) which break down and remove VOC’s from the air.

An example of some of the best technology to improve IAQ is the i-team i-air Pro, a high capacity freestanding air purifier designed for commercial environments.

The i-air Pro combines the highest available levels of MERV19 rated filtration (MERV19) with carbon pre-filtration and UVA/UVC + PCO technology in a self cleaning “kill chamber” designed to neutralise airborne bacteria and viruses.