Junker, you're probably thinking of the "How Stuff Works" episode on lead.
This is a condensed version of the battery recycling segment, from the larger episode:
Battery Recycling
That particular clip doesn't show it as clearly as the entire segment does, but there are a few not-so-obvious safety measures in the operation:
1. As soon as batteries arrive on-site, they go into the "lake" to remain wet. The acid lake and water spray help minimize any airborne particles.
2. Everyone on-site is supposed to be wearing a chemical respirator (not just a particle mask).
3. During the grinding process, everything still remains wet.
4. During the smelting process, access to the blast furnace area is tightly controlled, and personnel in the area must have an appropriate chemical respirator and suit.
5. Areas around the furnace and casting line have massive amounts of air flow.