"Mark L." wrote:
Edwin,
One of the recent wood mags (not sure which one) says PVC is not good
for DC. Just can't remember why not. I know it's easy to just glue up
and you're ready, but I would like to know why PVC won't work.

Well, some believe that the PVC can accumulate static electricity,
then discharge (by means of a little electrical arc) and ignite the
dust, thereby causing your own rendition of a grain silo explosion.

These are probably the same people who turn off their cell phones when
the fill up their cars with gas to prevent the deaded "cell-phone gas
station explosion"; because... well... gosh... even though we've never
tracked down a documented/verified case of it happening, it *must*
happen a lot because everyone talks about it, right?

Ugh. That's it! I'm submitting this one to MythBusters
(http://dsc.discovery.com/fansites/my...thbusters.html).

To answer your question, the May 2003 issue of American Woodworker
(page 54) has a section on setting up DC in your shop. The guy
suggests using steel instead of PVC for a variety of reasons. *One* of
the reasons is static buildup... but even then, the guy doesn't say
that there will be an explosion. He merely talks about the zap you can
get *yourself*. The other reasons are that steel comes in larger
diameters than the 4" where PVC generally stops at.

Strangely, he didn't mention how great steel looks when you
accidentally bump a tool into and dent it... or how yummy it feels
when you slice your hand on the sharp steel ends... or how the
sheetmetal screws protruding into the tube help the airflow!

He does point out though that, at large diameters, the price
difference between PVC and steel starts to become a non-factor in the
decision process.

Issue 13 of ShopNotes has an article about building your own cyclone
and collector. The seem to use all steel.

I recall reading some article about a week ago where the author went
into 4 more-likely fire hazards in your DC system than static
electricity. One of them was hitting a nail (or other metal) which can
cause red-hot sparks to go wafting through your DC system to the
collection bag. There were a couple of others. If I track down that
article, I'll come back and post it here.