Vacuum Pump Flash Fire

What Happened?

A new graduate student researcher was cleaning up after finishing his experiment. As part of the clean-up he decided to change the oil in the vacuum pump he just used.  The vacuum pump was a typical laboratory mechanical rotary-vane vacuum pump with a belt connecting the pump to a motor. When student drained the pump oil he noticed that it was quite dirty; he asked another graduate student for advice. The second graduate student suggested washing out the oil chamber with solvent. The new graduate student added pentane to the pump and turned it on to agitate the oil chamber. Immediately, a large fire ball erupted from the pump, but fortunately the graduate student was not burned.  No fire extinguisher was needed as it was a flash fire. After the fire, the graduate student reported the incident to his research advisor.

What Was The Cause?

Pentane is extremely flammable with a boiling point of only 36 oC and a flash point of -49 oC. The vacuum pump was likely still warm when the student poured pentane into the oil chamber emitting a large vapor cloud from the top port. When the electric motor was turned on, a spark from the electric motor ignited the vapors.

What Corrective Actions Were Taken?

  • Co-workers immediately came to assist the graduate student when they saw the fire
  • A fire extinguisher was available to extinguish the fire and the graduate students were trained
  • The incident was reported to the research advisor
  • The incident was discussed at the next lab meeting
  • Proper procedures for vacuum pump use and maintenance were developed
  • Importantly, flushing of oil chamber is done with clean oil, never with solvents

How Can Incidents Like This Be Prevented?

  • Labs should have written procedures for proper use and maintenance of lab equipment
  • Researchers should be trained to evaluate the hazards and risks of all chemicals and equipment whenever they start a new procedure



  1. If needed, use either ABC (dry chemical) or BC (carbon dioxide) fire extinguishers on flammable liquid fires
  2. Report incidents to your supervisor


Mechanical Vacumm Pumps

  • Electric motor creates sparks
  • Belt guards must be in place
  • Flush only with clean oil
  • Often leak oil; operate in pans