When it comes to air filters, it's important to make sure that they fit properly. If the filter is too small or too large, air will flow around the filter instead of through it, and not all of the air will be filtered out. To ensure that your AC filter fits perfectly, you should be able to easily install and uninstall the filter effortlessly, and the filter should not be small enough to move freely within your unit. Air filters have arrows printed on the sides that show how they are supposed to be installed.
These arrows should point in the direction in which the air flows through the system, which is away from the supply ducts and (normally) to the blower. It is important to note that there is no need for a hermetic seal between the frame and the air cleaner. However, it should be quite tight with a small amount of space around the edges. If you need to force the filter into place, you probably need a different size.
The goal is for the filter to slide comfortably in the frame with a little wiggle room, but not too much. If you live in an older home, with a non-standard size air return frame, you can use a foam weatherstrip tape to slightly increase the dimensions of your preferred filter or order a custom-sized air filter. Washable air filters are reusable versions of normal flat panel or pleated filters. You can find the recommended filter size for your unit model here in the table titled “Find your air conditioner and oven filter by make, model number and size”. The most affordable air filters often use material such as fiberglass that covers the filter structure, trying to filter out particles that pass through. You can also choose not to use factory-installed filter grids and have an HVAC professional install an external filter grid to get a coarser filter.
If the return grille is in the ceiling, you may prefer to use a filter that has a slightly larger actual size, so that the filter doesn't fall on you when you open the vent. An electrostatic air filter is a filter that has been charged with static electricity, trapping small particles such as mold and bacteria and keeping them in place, improving the efficiency of the filter. These high-tech electric purifiers use static electricity to filter particles from the air, like a much more advanced version of an electrostatic filter. Typically, you'll see filters with a MERV of less than 4 in residential ovens, window-mounted air conditioning units, or as a pre-filter in commercial units that need multiple filters. The filter in your air conditioning unit keeps the air in your home clean and should be replaced every 3 months. Note that if you decide to cut off an air filter, you should know what you're doing and make sure that the filters you use aren't weakened too much from the cut.