Most all our woodshops have some amount of dust in the air. It should not be a problem with some settling into your epoxy but you would not want someone dropping shaving from some their project onto your boat. I once used a jigsaw and did not pay attention to how far the high powered tool was throwing wood chips. Right onto a boat beside me with fresh epoxy on it. You will be sanding it all down for the varnish anyways. Then you will need to find a better place to varnish or just have it sprayed by a professional