The nominal size of an air filter is the rounded value that is used to label it. This size is different from the actual size, which corresponds to the exact dimensions without rounding. All filters come in two sizes: an actual size and a nominal size. For 1 and 2 air filters, the nominal size does not include the notch, while for whole-house filters, the nominal size is the rounded size.
Different manufacturers cut their whole-house filters into different sizes and then round them up according to standardized measurements. If the filter is too small, it will be loose and some of the air (and debris) will not pass through it. On the other hand, if the filter is too large, its frame will wrinkle, airflow will be restricted, and longevity will be compromised. Choosing the right air filter size is important to ensure that it fits properly and that particles suspended in the air are filtered out. If you select a filter that is too small, it won't fit properly and particles suspended in the air could pass through it, decreasing air quality and potentially damaging your equipment.
If you have one or two air filters that aren't on this list, you probably need a custom cut. To understand the size of air filters, you must first understand that there are two main types of air filters: household air filters and boiler filters. Household air filters are those that penetrate the wall when air returns; although, in some homes, they can enter the ceiling or the ducts themselves. Choosing the right boiler filter size not only extends the life of the boiler, it also helps to maintain excellent indoor air quality. The shift to the use of air filters made from sustainable materials can contribute to better environmental conservation. If the dimensions are too faded to read or if there's no air filter in sight, it's time to measure it yourself.
Filters 1 and 2 are trimmed by a quarter of an inch to provide little room for maneuver and ensure that they fit into the air return without being too large. The fact that the filter folds extend horizontally or vertically will not affect its efficiency. An expert on domestic air filtration topics such as HVAC filters, filtration efficiency, and indoor air quality can help you make sure you select an appropriate filter for your needs.
