Azobisisobutyronitrile Fire

Explosion and fire occurred in a lab in X Hall. A graduate student was thrown four feet and cracked a rib.  Her hair was singed from the fire ball. She was heating dioxane, a flammable solvent, and azobisisobutyronitrile on a hot plate in a glove box when a leak was suspected to have developed in the box. The hot plate’s thermostat probably served as the ignition source. She did not have the SDS for azobisisobutyronitrile and she was unaware that upon heating this chemical produces an acutely toxic chemical, tetramethylsuccinonitrile (TMSN). TMSN is immediately dangerous to life and health (IDLH) at 5 ppm. For comparison, cyanide gas has a IDLH at 25 ppm. 

Personnel from the Health and Safety Office entered the room to retrieve coats and open the windows not knowing the presence of this chemical. Their selection of personal protective clothing was insufficient to protect them from the TMSN. Both became ill from exposures. 

Description of Incident

The experiment involved heating 300 mL of dioxane, 30 grams of N-isopropylacrylamide, and 6.24 grams of azobisiosobutyronitrile ("VAZO" 64) in an inert atmosphere, on a hot  plate. Early in the experiment the student suspected there might be an air leak because the gloves which normally were inflated were sagging. The graduate student spilled approximately ten mL. Working within the gloves, she wiped up the spill with some paper toweling. Suddenly, with no warning, the reaction exploded and threw her three to four feet into the bench behind her. 

Another student phoned Security and the Environmental Health & Safety office.  He  evacuated  the hallway and all the adjacent labs, grabbing the book of MSDSs before leaving. She informed the Health and Safety Office of only three of the four chemicals that were involved in the incident. The company had never sent her a MSDS for  "VAZO". She was  visibly shaken and her eyelashes and hair was singed. The Health and Safety Office recommended that she shower, change clothes, and get a medical examination. The weather was freezing and students were requesting their coats, laptop computers and other belongings from the affected area. 

An employee from The Health and Safety Office entered the lab with a half face respirator with organic vapor cartridges to shut down the experiment, retrieve personal items, and open windows. The Health and Safety Office found that many of the windows which had been designed to open were sealed shut.  After about 20 minutes, a pane of glass was broken for ventilation.  

An emergency response team from X was called after several hours to appraise the situation because of the persistent smell.  The emergency response team wore Self Contained Breathing Apparatus (SCBA).

Neither student experienced any chemical exposure symptoms, although both were examined by physicians. The student involved in the explosion did crack a rib as a result of her impact with the counter.  

The next day the student was interviewed again. She informed the Health and Safety Office of  the chemical she neglected to mention the day before. The missing chemical was the azobisiosobutyronitrile or "VAZO" 64.  She thought it was causing the residual smell in the room. Researching the chemical, The Health and Safety Office discovered that upon heating the "VAZO"   readily converts  to Tetramethylsuccinonitrile,  an odorless chemical that is highly toxic and can be fatal in very small doses.   

Concentrations of Tetramethylsuccinonitrile are Immediately Dangerous to Life and Health (IDLH) at five ppm. [For reference NIOSH lists Sodium Cyanide, gas, at 25 ppm, both by inhalation.] Both health and safety office personnel who had entered the room experienced temporary symptoms from exposure to the Tetramethylsuccinonitrile that had penetrated their cartridges. 

Conclusions

  • The heating of flammable solvents should be done  so as to avoid any contact with ignition sources. An explosion proof hot plate is recommended for future experiments. The glove box is unsuitable for the use of flammable liquids due to the factory installed electrical outlets. Due to the air leak, all the elements were present for the fire ball that resulted.   Students should have researched each of the reactants and had a thorough understanding of their properties and decomposition products.
  • The Health and Safety Office should not have entered an area that has an unknown atmosphere.
  • Students possession should never have been taken from the room without being decontaminated.  These items were collected for cleaning.

Recommendations

  • In the future, an explosion proof hot-plate and a non-electric balance should be used. 
  • The glove box manufacturer should be contacted and asked if the box is acceptable for use with flammable solvents. 
  • A written standard operating procedure (SOP), that includes safety procedures, should be developed.  The SOP should  demonstrate a thorough understanding of all chemicals involved. SOPs should be reviewed by students and supervisors.  
  • Provide closer supervision of graduate students. 
  • After incidents similar to  this one the contents of the room should stay undisturbed until a thorough evaluation is completed.  
  • No chemical should be used until the MSDS is obtained and reviewed.