Unfortunately, the link at the end of the following citation no longer
works, but it did when I excerpted the article a couple of years ago.
A research scientist at MIT has looked into this matter very carefully,
both anecdotally and empirically. In the summary of his quite long
report, he says:
"...I have read more than a dozen research
papers on this topic recently. The thing I am most struck by is how
hard these guys have to work to get dust explosions in the lab. It is
not hard to get ignition if one makes a very carefully controlled,
nonmoving cloud with just the right dust mix, and introduces a spark
from a very carefully designed sparking mechanism. But no one seems to
be able in lab sized experiments to get electrostatic discharge
ignition of even very highly combustible dusts in remotely realistic
situations, and they do try. Is is possible? I presume so, but it is
"...there has never, to my knowledge, been a documented case of an
explosion problem with PVC in the home shop or a case of an explosion
in a filter bag in a home shop. A friend of mine who is a professional
cabinet maker asked his fire inspector what he thought about the hazard
of PVC ducts, and the fire inspector said he was far more concerned
about people keeping lighter fluid under the kitchen sink. The fire
inspector was intrigued and checked whatever registry of fire
information he had available and came back and said he could not find
one reference to a problem in a small shop with PVC ducts."
"In all the years that this has been debated on the Web, not one
verifiable report has surfaced of an exploding home shop dust
collector. I know full well that anecdotal evidence does not make good
science, and just because I don't know of a problem caused by an
electrical discharge in a home shop DC does not make it impossible.
But, such evidence is certainly food for thought, and at least shows
that such events, if they exist at all, are very rare."
Near the end of the report, there is an explanation of several common
MYTHS (untrue, unfounded beliefs) about home workshop dust collection.
That list (without the accompanying explanations) is as follows:
Myths--the following assertions are NOT true
1. PVC ducts are dangerous. FALSE
2. You can ground PVC. FALSE
3. The only thing of concern in a dust collector are the ducts. FALSE
4. The external ground wire works by reducing the static on the outside
of the PVC. FALSE
5. The external wire must be bare. FALSE
6. Grounded screws can not help as they are too far apart. FALSE
7. Grounding works by removing charge from the dust. FALSE
8. Metal ducts keep the dust from charging. FALSE
9. Any spark will ignite the right dust mixture. FALSE
10. Grounding PVC works by removing charge at a point, and since charge
must be uniformly distributed, it therefore removes charge everywhere.
11. Getting a discharge outside the ducts, say to your finger, means
you also have discharges inside the ducts. FALSE
The full report can be found at:
Click to see the full signature.