Glass Flask Rupture During Ozonolysis

Key Instruction Points

  • Review risk assessments when scaling up reactions.  

During an early attempt to scale up a procedure, a laboratory worker introduced ozone gas into a flask containing a small amount of organic material. The flask was set in a fume hood in a cooling bath designed to lower the experiment temperature to -85° C, 15° C below that which is normally used for such experiments. The sash of the fume hood was completely raised.  During the procedure, the worker noticed that a deep blue color had developed in the flask, an indication that the concentration of ozone was increased. He attributed it to poor mixing and had started to increase the stir rate when the flask exploded. Flying glass embedded into his face, neck and safety glasses.  

The worker did not experience any injuries to his eyes. Many of the cuts on his face and neck required stitches. Shards of glass were imbedded in the safety glasses. 

The sash of the hood might have provided enough of a barrier to avoid injury. However, most sashes are not designed to protect against explosions. Shielding should be used around any experiments that might explode. A face shield would have protected the worker from the cuts on his face and neck. Carefully evaluate the hazards before proceeding with a scaled-up experiment.​