Brooks Tanner replies: Please ground your system. Sawdust traveling through a tube acts as a Van De Graaff generator. The static charge is incredible.
I have in the past I used a plastic hose from my dust collector to clean out the bottom of my saw. If I did not keep in continuous contact with the saw, which is grounded, I would draw an arc that was actually painful. This plastic hose was only 12 foot long. Sawdust within the tube is extremely explosive due to the small bits of wood being lofted and surrounded by air. One small spark can ignite the mixture into a significant explosion.
In my shop, I use grounded metal pipe for ducting. Previous to this, when I was a hobbyist in my basement, I used PVC pipe. In this scenario, unshielded, grounded wire should be run inside the pipe to drain the charge.
If you run an un-grounded system you may be lucky and never have a problem. However, if you do have a problem, you could loose your house and possibly your life. It only takes a few minutes – be safe.