The simple answer is "never" in the house.
Yet, almost none of the 500+ questions that beginners have (and SHOULD have) are one-dimensional items. You wanna do this stuff outside. And yet, another poster was checking a reaction beaker the other day and a gust of wind blew a load of chlorine (I surmise) in his face. It knocked him to his knees and he had to go to the hospital. That might be an expensive lesson, in terms of dollars and cents and time. It could also DESTROY HIS LUNGS and KILL HIM. Reactions run outside are subject to outside temperatures, which can have a non-trivial effect on reactions, and not just the speed of reaction (although that is certainly the main area impacted) There are very, very few things one does in the area of refining metals that do not have secondary and tertiary effects. And they are sometimes subtle, sometimes dramatic. So when people on this forum hear an isolated question from an admitted noob, it cause concern.