Try putting a cigarette butt into the shop vac and see what happens... We desidn and sell industrial dust collection systems, so I have some background here. Sawdust is quite explosive in the right mixture. I would not recommend plastic ductwork although some will disagree. Why risk it? Also it is not as much a concern unless you are recycling the air. Certainly in most home shops with the bag type collectors (Penn State, Jet, Delta, etc...) i would recommend careful grounding and no smoking. With these reasonable precautions the risk is minimal.

> Doesn't it seem strange that you can get dust collection systems
> using plastic piping with ground cables strung through them, but many
> shop vacs, as far as I know don't?

> Mike Spence