Mom is typically not alone, but Dad is often preoccupied, and I may not be right there when SHE decides to get dinner going...while I live with them, I do work and am not home until after 5. She has shown signs to give me some concern, but not on a continuous basis. EX: putting a plastic meal tray meant for the microwave into the regular oven causing it to start to melt. As I was tired of cooking and leftovers going down the drain uneaten, I bought a nice set of 4 plastic sectioned dishes meant for the microwave with lids that fit snug and had vents. Well, I discovered tonight that one was missing, hunted it down to find it in the trash, and as I was washing it saw a spot that looked melted. Hmmm. But then I saw the back of it: It was a bigger melted spot, and the pattern in the area was a match to the oven liner mat...and there was a tiny piece of tin foil melted into it...when I looked in the oven I saw a small fragment of foil on the mat...So, I have read others have dealt with this by throwing the circuit breakers. I'm wondering if anyone has any other ideas, if you have used any sort of locking mechanisms, if you have invested in installing a killswitch (and how expensive is that, and how has it worked out) or if you know if any of the new ovens have some safety mechanisms built in, like needing a code to work. She is still quite functional in many ways. But she can be miserably stubborn.