I'm not a chemist or a physician, but from what I understand, epoxy (especially the hardener) is a sensitizer. Different people display different reactions to uncured epoxy contact. One common reaction is a poison ivy-like rash. The key is that with repeated exposure over time an individual's reaction can become much more severe. One factor working in our favor is that when we apply epoxy to a hull, most of the epoxy stays on the hull rather than in the air (there aren't a lot of evaporating solvents as with paints and varnishes)

An exception to this characteristic, which I think Bill noted, is that sanding less-than-fully-cured epoxy can put epoxy dust in the air and you REALLY don't want to inhale any of that. Once it is fully hardened, protection against sanding dust follows pretty much the same procedure as for any other woodworking dust.

Now here's the kicker, a very few individuals are highly sensitive to the limited fumes epoxy gives off and a few develop severe reactions after only limited exposure. If you're working in your home and a family member is one of those individuals you have a big problem.

What is a prudent kayak builder to do? I'd say that if you're building one boat (that limits everybody's total exposure) and considering the very limited amount of evaporation epoxy exhibits, a good exhaust fan in a basement window should maintain an airflow FROM the rest of the house INTO the basement rather than the other way around. As other writers indicated, it's not entirely clear what type of filtered mask is appropriate for the builder himself to wear; if epoxy MSDSs in general indicate an organic solvents charcoal filter I'd go with that. The times to be most diligent are when coating the whole boat as in wetting out and when filling the 'glass weave.

Mike Scarborough
Friendship Kayak