I have a couple of 3M 6300 half-face mask and a 3M 6900 full-face mask.
These models come in sizes (the 6300 & 6900 are large size). THey'll accept
a variety of filter elements and are, for me, reasonably comfortable. The
full line is available from industrial safety outfits. I wouldn't think
you'd want the full-face style for dinghy building. I got mine for grinding
glass tabbing in enclosed spaces. If you're going to use rolled/brushed LPU
paint or epoxy primers, get some organic vapor cartridges.

Don S wrote:

Hello folks,

I'm building an s&g pram, and I don't particularly like the idea of
filtering out the 'glass sanding dust with my lungs. I have one of
those big, cumbersome masks with interchangeable elements, but it gets
in the way of my glasses, and I'm less inclined to sand through the
fabric when I can see what I'm doing. I've tried both the throw-away
paper masks and a nuisance mask with the flapper valve for exhaling
(which also gets in the way of my glasses, but not quite as bad as the
big mask), and no matter how much I cuss and massage those metal
strips that are supposed to conform the mask to my nose, I can't make
them work. Exhaling with either fogs my glasses. I'm assuming that if
the air goes out that way, it must come in that way, too. In fact, I
can feel it entering when I inhale. As far as I can tell, I don't have
a misshapen shnozola. What's the trick?

Thanks,
Don