* Fits most furnaces and return grilles.
* Poor filtration efficiency at the sub-micron level (PFE1).
* Average filtration efficiency at the 1-3 micron range (PFE2).
The True Blue MERV 11 Allergen Air Filter is a 1-inch deep pleated filter. The 20″x25″x1 version we tested contained 22 pleats. Its filtration efficiency was similar to the Lennox X6673 with one caveat. It’s rated at three times the pressure drop, which would result in both more homeowner’s maintenance and higher energy (and general operating) cost.
It would also require frequent replacements due to its high pressure-drop and low depth. As for filtration performance, as the X6673, the True Blue MERV 11 filter performs poorly at the sub-micron range (25.4% @ 0.3-1µm) offers mediocre performance at the 1-3µm level (65.8%). It performed slightly better than the X6673 at the 3-10µm level (86.8%). Please note that Fltest.org does not incorporate this category (3-10µm) into our total score weight.