Certain makes and models of heating pads have been proven to overheat to the point of catching fire. Under UL standards no heating pad should get hotter than about 200 degrees. This is way below the point of ignition of any bedding materials. Even folded and crammed under the covers this should not have happened. However, I have seen it many times. Also, even if turned off, but if plugged in, there are some energized components in the controls of some heating pads. I would seriously question whether the pad in fact was off, but under certain circumstances that could be true, but if plugged in and a fire may still result.
That's great, but this thread is 3 years old. Please pay attention to the dates when posting.