? It says no long term effects from inhalation, does it not? I’ve never worn a mask.. which by mask I would assume you mean something more heavy duty than a dust mask. — but regardless if you can crack a window in the pin room or limit your naphtha session to a couple minutes you shouldn’t have any issues. Totally my opinion of course, but esp. after seeing the msds I don’t see a major issue with a bit of naphtha