I've never really worried about lead fumes. But, when I'm smelting, be it wheel weights or other lead, I provide good ventilation and try to stay up wind and out of any smoke. I avoid eating, drinking, smoking and rubbing my eyes, lips or other -----! If the lead looks to be oxidized I try to disturb it as little as possible. We are probably in more danger from depriming a lot of brass and from whatever dust comes from the tumbler. Good hygiene and common sense should keep us safe enough.