Shocking

I don't quite understand how my electronic furnace filter is supposed to work. It doesn't really seem to trap much dirt; it just makes a zapping noise a lot (much like a bug zapper). When I went to clean the filter yesterday, despite having the thing switched off, it sent a nice deep shock up my arm. It felt like I had slammed my funny bone into a 2x4. I finished the job wearing rubber kitchen gloves (mine are pink).

That's not my arm, nor my furnace. This image is from FilterUSA.com and this gentleman is doing the smart thing -- converting the evil electronic filter to a regular one.