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Supposedly electronic air filters work by ionizing dust (small airborne particles) and then attracting them to filter plates of the opposite charge.

What I don't understand is why the filter plates don't just reverse the charge on the dust, repelling them back into the airstream?

I'm thinking back to basic physics where an uncharged pith ball was initially attracted to a static conductor: as soon as it makes contact the conductor charges the ball and it is repelled by the like charge.

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The collecting electrode is grounded - so while the particle may be discharged, it will not get the opposite charge and be repelled again. They add tackifier as well to help the particles stick better. But you do need to clean the collector frequently or it will stop working. See http://www.epatest.com/EdArticles/PDFs/IAQ.pdf

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  • $\begingroup$ Ah ha: so ultimately the electronic filters depend on mechanical, not electrostatic, adhesion to keep the dust out of the airstream? $\endgroup$ – feetwet Mar 10 '15 at 15:18
  • $\begingroup$ @feetwet - I think it's a bit of both. Did you read the link? $\endgroup$ – Floris Mar 10 '15 at 15:19
  • $\begingroup$ Yes, and the section on electrostatic filtration only hints that the tackifiers help hold the attracted dust. It certainly doesn't suggest or explain how, in the case of electrostatic filters, the mechanical adhesion overcomes the electrostatic repulsion that I assume is produced when the dust makes contact with the electrostatic filter fibers. $\endgroup$ – feetwet Mar 10 '15 at 15:49

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