How does the MERV compare to dust spot efficiency?
The MERV rating is a Minimum Efficiency Reporting Value, as described in ASHRAE standard 52.2. Dust spot efficiency, as measured by ASHRAE standard 52.1 depends upon several factors including configuration and test velocity. ASHRAE 52.2 and 52.1 are designed to provide two different types of information and at the present time one does not replace the other.
