A lot of the time I'll see recipes call for heating non-stick on a medium- or medium-high flame with so little fat in ("one teaspoon of oil" or some similarly-way-under-enough quantity) them that it only covers like 1/4 or less of the pan surface, so most of the pan is heating dry, which AFAIK is a great way to turn the coating into a gas that's fairly bad for you. Though maybe that's folk-wisdom and it's actually fine to heat a nonstick pan empty? IDK.