When it comes to air filters, there are a lot of numbers to consider. From MERV ratings to FPR values, understanding the numbers associated with air filters can be confusing. But with a little knowledge, you can make sure you're getting the right filter for your home and lifestyle. MERV ratings are the most common way to measure the efficiency of an air filter.
The rating stands for Minimum Efficiency Reporting Value and is a number between 1 and 16. The higher the number, the more efficient the filter will be at removing particles from the air. FPR values are another way to measure filter performance. FPR stands for Filter Performance Rating and is a number between 1 and 10. Filters with an FPR of 4 are considered “good filters” while those with an FPR of 10 are considered “premium filters”. When it comes to size, all filters have two different measurements: actual size and nominal size.
The actual size is the exact dimensions without rounding while the nominal size is the rounded dimensions of the filter. For air filters 1 and 2, the nominal size does not include the notch while the actual size does include it. For whole-house filters, both the nominal and actual sizes are rounded. Neutral density (ND) filters are also important to consider when it comes to long exposure photography.
ND filters reduce light intensity without changing color or hue. They are measured in terms of how many “passes” they make through a filter. An ND0.3 is a 1-pass ND filter while an ND0.9 is a 3-pass ND filter. It's important to remember that different manufacturers cut their whole house filters to different sizes and then round them to standardized measurements. This means that two 20x25x5 whole house filters made by two different manufacturers are probably not the same size. When choosing an air filter, it's important to consider your lifestyle and personal environment as well as the size of your air conditioner and oven filters.
Make sure to change your filter on a routine basis so that your system runs smoothly for years to come and your indoor air quality is excellent.