In most cases, you should be able to use the closest standard size for your air filter. Stacking filters is not recommended as it can restrict airflow and cause your oven to run inefficiently. Oven filters should fit snugly, but never be forced into position. If you have to force the filter into its slot, then it is too big and can damage the filter or reduce its effectiveness.
It is important to remember that filters should be slightly smaller than their slot to allow for easy removal and installation of a new one. In some cases, you may need a custom filter for your HVAC unit. If you have to jam the air filter to install it, try a different brand of oven filter or a custom-sized air filter with a slightly smaller actual size. The nominal size of an air filter is not the same as the actual size, so it is important to measure the filter with a measuring tape or ruler before purchasing.
For common brands of HVAC systems such as Goodman, Lennox, Trane, Rheem York, Coleman and Carrier, most standard air filter sizes will work. If an air filter is too small, this will create air gaps and contaminants will avoid filter material. For air filters, the dimensions of length and width are interchangeable, although conventionally the largest of the measurements is the width and the shortest is the length. When it comes to air filtration, many people are confused and don't know where to start when it comes to finding the right size for their system.
To ensure that you get the right size for your system, measure your existing filter with a measuring tape or ruler before purchasing a new one. This will help you avoid costly mistakes and ensure that your system runs efficiently.