When it comes to air filters, size matters. To ensure that your filter is working properly, you must obtain the correct dimensions. The nominal size of the filter should be rounded to the nearest whole number, and the actual size should be 0.25 to 0.5 cm smaller than the slot or frame. MERV stands for Minimum Efficiency Reporting Value and it is used to measure the size of air particles that an air filter can trap.
A higher rating indicates that the filter can capture smaller particles. If you live in an older home with a non-standard size air return frame, you can use adhesive foam waterproofing tape to slightly increase the dimensions of your favorite filter or order a custom-sized one. Incorrectly installed or improperly sized filter frames can cause air leaks, significantly reducing filter efficiency. Do not stack several small air filters on top of each other to fit in a larger air handler. Most people won't be able to find the size of air filter they need at the local home improvement store. The MERV scale was designed to provide a balance between particulate filtering and energy efficiency.
To make sure that the next filter you buy is the correct size for your system, you must measure the interior dimensions of the air filter inlet. There are several great options for buying air filters online and getting them delivered to your doorstep. The higher MERV rating means an air filter will capture more dust, while the lower rating means a filter will capture less dust.