A square 23x23x1 nominal opening takes a filter measuring 23" x 23" x 1" actual, which is what this Aerostar is built to. Odd-sized square returns in the 23-inch dimension show up on certain residential systems and in custom installations where the original installer used a non-standard grille opening. MERV 8 covers standard household dust and pollen filtration. MERV 11 captures pet dander and most common allergens. MERV 13 handles fine particulates including bacteria, virus carriers, and wildfire smoke - the recommended grade for households with respiratory health concerns. Pleated synthetic media with an electrostatic charge built into the fibers handles the filtration. The pleats provide substantially more surface area than a flat fiberglass filter would at the same nominal size, which extends the service life to a 60-to-90-day window under typical residential conditions. The electrostatic charge improves capture of sub-micron particles where mechanical filtration alone reaches its physical limits. Manufactured by Con-Air Industries in Orlando, Florida. The cardboard frame is reinforced to maintain shape under blower suction. MERV 13 in this depth wants a 30-to-60-day change interval because higher filtration grades reach their pressure-drop limit faster than lower MERV options.
