Deflagration and Fire from Malfunctioning Lab Stirrer/Hot plate
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Type:  Lessons Learned

Publisher:  Oak Ridge National Laboratory, Oak Ridge, TN (ORNL)

Date: 

Topics:  Fire Protection, Laboratory

An electronically controlled combination electric stirrer/hot plate located in a fume hood in a chemistry laboratory at ORNL spontaneously malfunctioned, energizing the hot plate to its maximum temperature even though the heater switch remained in the OFF position. This in turn heated a chemical mixture in a round bottom flask resulting in a deflagration and fire.

On Sunday afternoon, April 20, 2014, an employee entering the ORNL Materials & Chemistry building noticed smoke at the end of a hallway. The employee looked through the door to an unoccupied lab and saw small residual flames inside a fume hood along with extensive damage to the hood. Emergency personnel were called and ORNL Fire Department personnel extinguished the residual fire with a portable fire extinguisher. There were no injuries. Six persons were evacuated from the building.

At the time of the event (a Sunday afternoon), there was no activity in the laboratory. A researcher had been in the lab earlier in the day, but it was unoccupied at the time of the event. A round-bottom flask was located on a cork ring which rested atop a common combination stirrer /hot plate. Both controls were in the OFF position. The flask contained a combination of hexane, isopropyl alcohol, and small quantities of other chemicals which had been periodically stirred using the stirrer /hot plate. The flask had not been stirred for several days. The stirrer/hot plate heater had not been used at all for this process.

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