When it comes to air filters, there are a few key numbers that indicate their efficiency and performance. The most important of these is the Minimum Efficiency Reporting Value (MERV) rating, which ranges from 1 (least efficient) to 20 (most efficient). For residential use, anything above a 13 is usually unnecessary, unless you have a serious health problem. The higher the MERV rating, the more particles the filter captures, as the fabric becomes tighter.
For example, an 8 MERV filter will filter down to about 10 microns, while a 13 MERV filter will drop to about 0.3 microns. In addition to MERV ratings, filters also have nominal sizes. This number is usually shown on the side of the filter and is a rounded estimate used for consistency. All filters have an actual size and then a nominal size. The actual size is the exact dimensions without rounding; while the nominal size is the rounded dimensions of the filter.
This means that for air filters 1 and 2, the nominal size does not include the notch, and the actual size does include the notch. For whole-house filters, the nominal size is the rounded size, and the actual size is only the unrounded one. The size of your pleated air filter is always presented in a string of three numbers, where the first number represents the length, the second number represents the width and the last number represents the thickness. These numbers relate to the standard size of your home's return ventilation grilles, responsible for controlling the movement of air to and from your HVAC unit.It's important to note that there is no need for a hermetic seal between the frame and the air cleaner. Filters should be changed every 30 to 90 days, depending on their type and efficiency.
There are literally thousands of sizes of air filters available on the market today, so it's important to understand how to read these numbers in order to make sure you're getting an effective filter for your home.