Failure to label a waste stream mixes sulfur and an oxidizer, sets fire to waste bucket; fire threatens other chemicals during cleanup – March 2012

What happened?

A research group scheduled a laboratory cleanup for a weekend. Their plan was to remove old and no longer used compounds from the glovebox and to quench these materials. The planned quenching procedure used copious amounts of water for small amounts of compound, as outlined in the laboratory’s standard operating procedures (SOPs) for alkaline metals and pyrophoric materials. All other dry material was deposited into a five gallon bucket that was located on the laboratory floor.

As the cleanup proceeded, members of the group did not keep an accurate account of all material being disposed of in the waste bucket, and they did not check compatibility of the waste. Sulfur was added to the bucket and, sometime later, a metal compound was added, causing an exothermic reaction that resulted in a fire. The work team attempted to extinguish the fire with sand but tipped the bucket over. A team member grabbed another can of sand and extinguished the fire.

Smoke from the fire triggered the fire alarm. The Lubbock Fire Department (LFD) and Texas Tech Police Department responded. There were no injuries.

Area in fume hood where quenching was being performed.

Area in fume hood where quenching was being performed.

Area on floor in front of fume hood where dry materials were being collected in 5 gal bucket.

Area on floor in front of fume hood where dry materials were being collected in 5 gal bucket.

What was the cause?

A member of the work team put approximately a gram of sulfur in the waste bucket and covered it with sand. The researcher did not add sulfur to the list of compounds in the waste stream. At a later point, another member of the work team added a metal compound. The waste caught fire.

What caused the fire?

  • The metal compound reacted with the sulfur and the oxidation resulted in a fire.
  • Chemicals were not appropriately segregated.

What corrective actions were taken?

When fire and police personnel released the lab, Environmental Health and Safety (EH&S) staff found that chemicals and wastes, including those not involved in the incident, were not properly labeled, segregated or stored. These and other issues had been identified in the most recent laboratory safety survey. Therefore, EH&S closed the laboratory.

EH&S staff retrained the laboratory group in waste handling procedures and then worked alongside them to segregate chemicals and store them appropriately in the laboratory. EH&S staff reviewed and approved the glovebox procedures and lab SOPs, monitored cleanup of the clutter in the lab, and scheduled follow-up visits to review lab procedures and status. The faculty member met repeatedly with the department chair and safety committee chair, and with EH&S staff. The postdoctoral researcher present when the fire started was required to develop a waste protocol for what should have been done with the day’s waste stream. The lab was released to the research team after four days; follow-up visits continued over next month to make sure they were maintaining safe operating procedures.

How can we prevent incidents like this?

  • Conduct waste accumulation inside of fume hoods and not on bench tops and floors.
  • Label all waste streams as waste is added.
  • Prepare written waste handling SOPs that describe specific procedures for handling each waste – and use these SOPs when you prepare your waste.
  • Conduct lab cleanups and waste preparation during normal working hours.
  • Use EH&S staff as consultants when you plan to dispose of reactive wastes.
  • Segregate and store chemicals appropriately at all times, including waste disposal. Use color coding to help the lab worker keep chemicals separate.
  • Minimize clutter in the lab.

Resources

  1. Bretherick’s Handbook of Reactive Chemical Hazards, 6th Edition, P.G. Urben, ed., 1999
  2. Prudent Practices in the Laboratory, Handling and Management of Chemical Hazards, National Research Council, 2011 (http://www.nap.edu/catalog.php?record_id=12654).