Why do pleated air filters (such as 3M Filtrete) look cleaner at the end of 3 months than fiberglass filters?
I expected the pleated filter to look dirtier, since it is supposed to capture more airborne particles, but at the end of 3 months, it doesn't look anywhere near as dirty as a cheap fiberglass filter.
Anyone know why?
Imagine the filter paper stretched out: It will be at least twice as large as the filter with the paper still pleated. Three months' worth of dust, spread out over twice the area, looks like half as much dust.






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