A 20x30x2 nominal return takes a filter at 19 3/4" x 29 3/4" x 1 3/4" actual, which is the spec this Aerostar is built to. Two-inch filters in this size show up on older residential furnaces, some horizontal air handlers, and certain light commercial systems. The 2-inch depth holds roughly twice the debris of a 1-inch equivalent at the same nominal size, and the lower pressure drop is easier on the blower across the filter's service life. MERV 8 covers standard household filtration. MERV 11 handles pet dander, smoke residue, and most allergens. MERV 13 captures fine particulates including smoke from wildfires, bacteria, and virus carriers. Pleated synthetic media with an electrostatic charge handles the actual work, manufactured by Con-Air Industries at the Orlando, Florida facility. The cardboard frame is reinforced to maintain shape under blower suction. Service life is 4 to 6 months for MERV 8 and 11 in typical residential conditions, 2 to 4 months for MERV 13 under similar conditions. If you're switching from a 1-inch filter to this 2-inch unit, expect the change interval to roughly double. The deeper depth is also more forgiving on older systems where return ductwork wasn't sized generously.
