Teflon is hugely toxic to birds, I lost my first cockatiel this way years ago, before that was widely known. It was in a pretty open room too, one of those where the kitchen dining room, living room are all open to each other.
Since then we adopted a 'birds behind closed doors', method whenever someone is cooking on the stop top.
Id also recommend that whenever you visit someone elses birds, or handle birds from any other source you wash your hands before handling yours. Theres a couple diseases easily transferred this way.