I just wanted to add a bit to the discussion of using respirators. To put my credentials up, I have worked for the last 20 years in the hazardous waste cleanup field and am a certified hazardous waste site worker and supervisor and have led several OSHA complaince classes.
I agree strongly that a respirator should be worn when generating wood dust but with a few points. You should always check with your doctor first (OSHA requires a pulmanary test annualy if you use them at work). Respirators make it harder to breathe and have triggered heart attacks in people with athsma and emphasima (sp?).
If the mask does not fit, it does not do any good. A propper fit test is hard for the hobbiest to do but a quick and almost as good check is the following: With the cartridges off, hold your hands over the intake and breath in. The mask should get pushed in. If you feel air comming in, adjust it till it does not. Then with the cartridges on, cover the outlet valve and breathe out. The mask should inflate a bit like a baloon. No air should escape. If you feel cool air coming in while you are working, you have a leek. If it gets harder to breathe while you are working, or if you smell an oder (other than the rubber from the mask) your filters are loaded and should be replaced right away.
It does not do you a lot of good to use a mask and take it off when you are done and breathe in all the dust that is in the air. Walk out of your shop, close the door and let things settle for at least 15 minutes. If you have to, you can speed up the settling of dust by spraying the air with a plant mister filled with water. You don't want to get things wet, just let the water cary some of the dust out.
Just one more point, most hobbiest use what is called a half face respirator which covers you mouth and nose. A full face respirator also covers your eyes protecting them from fumes and dust. Most, but not all so check, full face resoirators use safety rated lenses so you have that protection too.