MERV is Minimum efficiency reporting value. in a simple word it tells about how the air filter handles PM particles in range of 10 micrometer to .3 micrometer in worst scenario. MERV is actually used in HVAC system to check the air cleaning efficiency. These ratings are also applicable on portable units. We can use these rating to understand the filter type used by the machine. In Portable Air purifier The MERV rating is in between (13-16)
MERV rating was developed by ASHRAE, The american society of Heating, Refrigeration and air conditioning engineers in 1987. They do several test on Air filters and create report which tells their minimum efficiency value in handling PM particles in worst scenario.