Rehd is correct, the dust would be too uncomfortable to breath. I dont know the PPM, nor do I think it is in the "dust collection bible", but I'll look tomorrow for you. In any event, explosion is not the risk in the general shop. In a dust collector, explosions are common where high dust loads and static electricity are combined, or where some nitwit puts his cigarette out in the DC intake. Or hooks the DC system up to a metal grinder. These are normally industrial applications, there is not a single documented case of DC explosion in a home shop from static electricity, even where PVC pipe is used. If you want to know more on the subject, there has been a great deal of discussion on the wood magazine board, www.woodmagazine.com. Go to the tool D-group and search for DC, or static.

The risk you are running is from breathing the particles of certain woods. Cedar, for example, is a known carcinogen. Redwood, too. For more on that, contact your local OSHA or equivilant safety agency, and get the allowable PPM concentration of sawdust for a furniture shop. It's the 10-micron and down ones that are particularly nasty, as they do not settle out of the air nor can you see them. You are probably in fair shape with the doors open, and pretty good shape with the doors open and fans blowing. Of course, good dust collection at source is the best policy, but until recently it has not been feasible for a home shop. And even now, there is an awful lot of crap out there. Talk to me, or read the WOOD board if you are looking at installing DC. It's what we do at Benz Air, and my boss is one of the best in the country. I've learned a lot by osmosis...

: I work in a shop which is 35 x 40 feet. I have built numerous cedar strip
: canoes etc. etc. I have started building hardwood strip hull & ribbed
: kayaks with treated canvas top, but I'm getting in trouble with WHMIS
: because of the dust. I have been doing this kind of work for over 25
: years.

: I believe in an open door policy which is an 8 x 10 garage door on each end
: of my shop. When I am ripping hardwood both doors are wide open to get rid
: of the dust. I have asked & asked but nobody can give me the parts per
: million before sawdust becomes explosive with the flow through ventilation
: that I have. Why is this not safe?

: Parts per million (what would it look like?) I have no idea, I would like
: some information because I cannot afford a dust extraction system.

: Thank you. Jake