A lot of early copper/bronze smelting in the Americas made use of arsenic alloys. They avoided inhaling the fumes by constructing furnaces in areas where the wind direction was predictable. I'm curious if ancient Mediterranean peoples had the same practice, or if they came up with another strategy.
Apropos of something, Ötzi the Ice Man showed high levels of arsenic in his tissues, attributable it is said to this very sort of smelting.
A lot of the time they didn't. It has been said that the story of Vulcan being lame is due to arsenic poisoning. You will remember that he was the god of the forge, roman equivalent of Hephaestus.