Air filters come in a variety of sizes, and it's important to know which size is right for your needs. The three dimensions that are used to label air filters are the length, width, and thickness or depth. It's important to note that the first number refers to the length, the second number is the width, and the third number is the thickness or depth. Whole house air conditioning filters typically range from 3 to 6 inches wide and can last up to 6 to 12 months, depending on environmental conditions.
If you're unable to find the size air filter you need at a local home improvement store, Lennox offers a MERV 16 filter option in their Lennox Pureair system. This filter is one of the most efficient residential filters available and is recommended as an upgrade for specific Carrier, Trion Air Bear, and Honeywell systems. Whole house filters usually go to an air controller, which is usually located next to the HVAC system itself. To reduce the number of unique air filter sizes on the market, always indicate the smallest measurement first instead of having a size of 20 x 30 and one of 30 x 20 as two different products.
If your current air conditioner filter doesn't have any size listed, you can measure the length, width, and depth of the filter and compare it to find the actual size of your filter with the corresponding oven filter size in an oven filter size chart (nominal size). When looking for a standard air filter size, it's important to remember that there are two main types of air filters: room air purifiers and HVAC filters. Room air purifier filters are measured by nominal size, which is a rounded number that varies by brand. Many filters have a part number of each brand they are compatible with in their list.
If you use a room air purifier and need to replace the filter, it's important to find the correct size replacement HEPA filter. The most common size is 20x20x1, which is easy to find and is in a short list of sizes that are common enough for air filter companies to keep in stock.