I have a central vac in the house. Today I was cutting a small section of the plastic piping out to install another line. As soon as the small manual hand saw I was using broke through into the pipe, I saw and felt a discharge from the saw to my hand. It hurt like hell! Thought I cut into a 120V line for a sec. I would have never believed it, but the static build up was intense. I had used the vacuum about 20 minutes prior to cutting the pipe. The vacuum sucks a lot of fine wood dust through those pipes! Think I might look into the grounding thing real soon.