Product review (5 stars): but we do regularly cook with small amounts of oil and these filters are good for about 90 days
These filters actually catch oils; we don't fry much, but we do regularly cook with small amounts of oil and these filters are good for about 90 days. When you remove them to replace them, no oil has passed through to the fan inlet. Recommended.  Buy two or three at a time, so you will have one to install when you think about it.