I started reading about the danger of using your DC for general shop cleaning. If you accidentally get something metal (unseen nail, screw, etc) it could hit the impeller casuing a spark which could lead to a nasty DC fire.... Given the high availability of various types of floor sweeping accessories is that an over blown concern? If not, do they recommend you clean up with a shop-vac before creating the pile of sawdust which you then send to the DC?
Ok, ok, time to dispel another urban legend. While it is technically possible for what you say to happen, it is extremely unlikely.
1. The "something metal" and your impeller will both need to be ferrous (iron or steel) or magnesium in order for it to generate a spark.
2. The speed at which the "something metal" would hit and be thrown clear of the impeller, reduces the chance of a big spark.
3. Any spark will will be quickly extinguished because (remember the fire triangle) the "something" metal will be hot but not burning and will be immediately cooled by the high velocity air flow in the blower (scratch one side of the triangle). Steel doesn't really burn, it just gets hot, the dust traveling through the blower is moving so fast and is of such low density it will not ignite, and the spark will have cooled sufficiently (below ignition temp) by the time it reaches the dust bin so it won't be able to ignite a fire there. (scratch side two)
4. You are much more likely to start a fire by vacuuming up a lit cigarette butt.
5. If you put a mini-cyclone before the blower you eliminate all chances of a fire.
6. You would immediately smell any fire since the DC is circulating that air. Any fire, however remote would be contained to the dust bag/bin and be of the smoldering type that could be easily moved outside.
This is not just theory. I have used my DC (steel impeller) as a floor sweep and vac for nearly 10 years. Being a tinkerer as well as a woodworker I work with metal all the time. I often suck up ferrous nails, screws, bolts, nuts, pieces of sheet metal, etc. (also tape measures, drill bits, chuck key, etc. :BangHead: ) with the DC. I have NEVER, EVER, had even the slightest indication of ignition from any of these. I have a cyclone, but it is plumbed AFTER the blower (push-through configuration) so all dust and metal debris hits the impeller full force.
Remember, EVERY single-stage DC has the intake right on the blower. I haven't looked at one lately, but if this were a problem, they would have caution placards up the ying, yang.
