Older hotplates with relay heater switches can spontaneously heat in the heater dial OFF position.Hotplates manufactured from 1960s – 1980s may still be in active use.In 2007, 2011, 2012, 2014 the University of California, University of Pennsylvania, MIT, and Oak Ridge National Lab issued similar safety advisories for Corning PC-35, PC-200, PC-220, PC- 351, Fisher IsoTemp and the Thermolyne Model:SP46925.In 2005, Lawrence Berkeley National Laboratory issued a safety advisory related to a Corning model PC 420 hot plate.Spontaneous and unexpected heating of hotplates has been the cause of laboratory fires and explosions.
