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Mercury Thermometer Broke and Exposed Students

What Happened?

Research students were using a mercury thermometer to measure the temperature in a laboratory oven and the thermometer broke. The students unplugged the oven and when it was cool, started disassembling the oven to remove the broken glass. They found drops of mercury and immediately stopped the cleanup. They realized that this hadbecome a hazardous spill incident, so called EH&S.

Mercury is hazardous due to a low but significant vapor pressure under ambient conditions (0.002 mm Hg at 25 oC / 77 oF). Hence, at elevated temperatures as in an oven it creates a major health hazard for laboratory personnel in the immediate area.

When EH&S arrived they assessed the situation and realized that this could require specialized hazardous material cleanup. Access to the laboratory was immediately restricted. Since it was an older oven and mercury had penetrated down to the coils area, the PI and EH&S decided to dispose of the oven entirely. The contaminated oven was then sealed in plastic wrap and sent out as hazardous waste. The research students were tested for mercury exposure.

What Was The Cause?

The students were not sure exactly what transpired, but the mercury thermometer was either knocked over, bumped against the metal oven racks, or dropped to a lower shelf. Regardless, the glass broke in multiple places spilling out liquid mercury. 

What Corrective Actions Were Taken? 

  • The PI discussed the incident and the hazards of mercury exposure with lab members.
  • The PI and lab members reviewed use of mercury thermometers in the laboratory and considered alternatives.
  • An SOP for mercury spills was prepared.
  • EH&S notified other laboratories of the hazards of using mercury thermometers in ovens. 

How Can Incidents Like This Be Prevented? 

  • Remove all mercury thermometers from laboratory autoclaves, furnaces, and ovens.
  • EH&S inspections of laboratories should look for mercury thermometers inlaboratoryautoclaves, furnaces, and ovens.
  • Never use mercury thermometers inlaboratory autoclaves, furnaces, and ovens. Non-mercury immersion thermometers come in a variety of styles and working ranges such that the range from -100 oC to + 250 oC can measured. 
  • Only use thermocouples with digital temperature readouts or handheld Infrared thermometers to measure temperatures in laboratory autoclaves, furnaces, and ovens.
  • If an older style oven will continue to be used, plug the thermometer orifice so that an unsuspecting future researcher does not inadvertently place in a mercury thermometer.




  1. Call 911 immediately to report major inuries or hazardous materials spills.
  2. Report all incidents to your supervisor.
  3. Report all laboratory incidents to the EH&S department.
  4. Whenever mercury is spilled, do not immediately start a cleanup. Instead, contact EH&S department for assistance making an assessment to decide the best course of action.