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Douglas Kosar from the University of Chicago recently performed testing to quantify the affects of the bypass of unfiltered air around a filter. Filters with different efficiency ranges were tested with varying size gaps to determine the efficiency losses associated with each filter and gap size. The results of the testing substantiate what we have believed and claimed all along. Lower efficiency filters did show efficiency loss but the loss was very minimal. A MERV 7 filter degraded to a MERV 6.
Higher efficiency filters showed a more significant degradation of efficiency. MERV 14 filters degraded up to 6 MERV values depending upon the size of the bypass gap – that means a MERV 14 can perform as low as MERV 8 levels. This has huge implications for hospitals and other sensitive applications. The importance of eliminating bypass with proper filter gasketing and examination of the filter housing or framing system for bypass is paramount.

Submitted by Duane Colwell,
Director of Marketing


Even the best air filter you can buy is only as good as designed IF it is sealed & installed properly. Here are some tips to help you get what you have paid for.
  • Cardboard framed filters should be taped. I find it eaiser to to use doublesided tape when cardboard framed filters are required to be used. This also makes it eaiser to remove the filters out of long tracks.
  • Use Self-Sealing filters whenever possable. This saves labor and budget dollars.
  • For metal framed filters use non-pourous gaskets to seal your filters. Most filter manufactures will provide gaskets, but they are pourious and become a very inefficent air filter. Sometimes it is best to purchase your own gaskets.