Pyromaniac roomba

[Evil Robot]

I have been thinking about getting a roomba since we have 3 dogs. Only one problem, we have a ground level fireplace. I have pictured a scenario where a roomba enters the fireplace somehow, catches fire, turns around and wanders the room. It would be driving around dripping buring plastic on carpet, under wood end tables, next to couches, etc. I know I could put an "invisible barrier" or metal bar across the hearth, but it would always be in the back of my mind that it would find the ashes to irresistable and find a way in, then a way out.