Here's how I set up so as to be able to cast indoors in my garage. Went to the builders' supply store and bought a bathroom exhaust fan. Built a box big enough to house the lead pot. Put the fan on top of the box and vented it to the outside. Welded an extension on the trip lever so I could reach it under the curtain. Flux the melt, hang the curtain on the box, and work without worrying about inhaling lead fumes. The pot is a Magma Master Pot and has a bottom feed.
If I had it to do over I would build the box about six inches taller as the top of it gets pretty hot after a couple of hours.