Using a melting pot and not open fire is the key. Lead is actually quite safe to work with even with just the most minimal procautions. By using a melting pot you will likely never to get lead hot enough to contaminate air. I am by no means saying do not use precautions. Please use them. Someone said something about water ....Think of one drop of water expanding to 300x its size in a blink of an eye the displacement of liquid lead will equate to about the size of a golfball being blown out of your pot...No good can come of that. Most people have enough common sense to not hurt themselves...Burns yes, no matter what precautions you take it will happen. BE SAFE...Some actual facts below..
Keep the temperature on the lead pot as low as possible. Lead melts at 621°F. Lead boils at 3180°F, but significant amounts begin to evaporate above 900°F. Any lead vapor quickly forms a very fine lead oxide powder and can be inhaled.