Air Filters: Build Your Knowledge of How to Choose and Use Them
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Air Filters: Build Your Knowledge of How to Choose and Use Them


Choosing which air filters to use in your home, as well as when and how to change them, is an important part of ensuring optimal A/C efficiency. Here are several factors for choosing and using air filters correctly in your Portland home:

  • MERV (minimum efficiency reporting value): This industry-standard measurement evaluates how efficiently air filters perform on a scale of 1 to 16 (with HEPA filters falling in the 17 to 20 range). MERV 1 to 3 removes only the largest airborne particles while MERV 14 to 16 removes nearly all of even the tiniest contaminants. For the average home, a mid-range filter between MERV 8 and 11 is usually best in terms of purchase price, efficiency and maintaining necessary airflow.
  • HEPA (high efficiency particulate air): Despite their ability to trap minuscule particles down to 0.3 microns, HEPA filters (rated MERV 17-20) are not recommended for HVAC systems without modifications. The weave is simply too tight to maintain the necessary airflow for efficient operation. Reserve HEPA filters for vacuums and room air cleaners.
  • Choosing the right size: Filters are usually sold under nominal dimensions, which are the actual dimensions rounded to the nearest inch. (An actual dimension of 10.5” x 20.75” x 1.25” translates to a nominal dimension of 11” x 21” x 1”.) Measure your existing filter and look for the closest match in nominal dimensions so the new filter fits snugly without being forced into place. Or easier still, just look at the frame of the filter you’re replacing to find the size you need.
  • Changing filters: While actual replacement times vary by filter and application, it’s recommended that you check the filter every month and change it after no longer than three months.
  • Washing or vacuuming filters: A bath seem like a viable option to extend the filter’s life, but filters don’t hold up well when wet. It’s also possible you might tear the filter if you attempt to vacuum it. In general, it’s best to keep the filter as is until it comes time to replace it. The exception is air filters specially designed for cleaning rather than replacement.

For more information about buying and using air filters in your HVAC system, please contact us at (503) 266-1249. Our experience serving the Portland area dates back to 1976.

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