Make a decision
Filter MERV versus filter fit
One scope
MERV describes particle capture under a test method.
The other scope
Fit determines whether air passes through the media or around its edges.
A concrete example
A MERV 13 filter that leaves a quarter-inch gap at the door can bypass. The same system may need a correctly sized rack before any higher-rated media can work as intended.
Which question settles it?
A higher rating with a bypass gap may leave the blower dirty; address dimensions and rack condition.