Roger that Bill. If you read the NFPA code on static electricity (OK the number escapes me at the moment) you will find you ALWAYS must run a conductor alongside your plastic piping in many hazardous or static prone areas.
Folks that are shooting sawdust through plastic pipes with no ground are living pretty dangerously. The power in one good spark can set up a very dangerous explosion.
I had to get into this very heavy when we did the fuel farm at Dulles, it's pretty amazing how much electrical buildup you can get with fuel running through pipes. The fuel never really touches the pipe due to differing polarity of fuel and pipe.
Pretty interesting, but a bit thick for quick answer.
