I never ever leave my washing machine on when I am out, even for a short while. My friend's sister-in-law left hers on for 15 minutes while she went to the corner shop - when she came back, the fire engine was outside the house - fortunately, a neighbour had seen the smoke in the kitchen and called them before it got too bad. Even so, the dog was unconscious and had to be rushed to the vet - if the neighbour hadn't seen the smoke, it would have been too late for the poor dog by the time the lady came home.