Topic: Dirty air filter test ??

[grcamna2]

I'm hoping someone may know if it's possible to test an air filter using light ? I have held up my paper O.E. style air filter to a good light & if I saw light through it I was a bit encouraged.I realize that this isn't a REAL flow test or anything like that...but I wonder if an expert can tell if he has looked through many air filters by holding them up to the light to see the amount of visible filter area that is still good? Can this give me a rough idea of the paper air filters condition generally speaking...?? I know that over time the paper can also harden even if the filter looks "visibly" clean under the light & hard(high humidity environment?) paper will not breathe as well as nice pliable paper w/ less damage.
                                                   Any ideas ?

[grcamna2]

I just wondered if it's possible to come close this way ?

[ADW]

Yes, that's a reasonable way to get a rough guess to your air cleaner's usability. I work for a large auto manufacturer and we've done testing on air filters to see when they really need replacement/when the flow is truly becoming compromised. You wouldn't believe how filthy the filters look well before they actually start becoming detrimental to airflow. So yes, if you can see light through it, it's likely still OK.

[grcamna2]

Thanks ADW; I appreciate your confirmation.

[Deltarider]

I have about five used paper air filter elements in the basement of which one - I remembered - was suspect. Out of curiosity I went down to do that light test. Four show light through the paper. One of them hardly. Guess what? When looking closer that's the one I had already scratchmarked with a cross on its side. So - although not very scientific - I'd say the test works.
In many years experience I've noticed that these filters live much longer than people think. For a vacation with thousands of km's ahead I would change the element for a new one, to be sure. I've always kept the old elements for reserve. Changing the element can be done in between 5 and 10 seconds.