What Happened?
A chemistry researcher was using an older model hot plate to heat an oil bath to 120-150°F. He borrowed the hotplate from someone else and was not familiar with the temperature controls. On this particular hot plate the temperature dial could go around from “LO” to “OFF” and back to “HI” heat. The researcher thought he had turned the hotplate “OFF” but it was still in the “ON” position and 30 minutes later the mineral oil bath ignited.