Peroxides are chemical substances that contain the reactive peroxo unit (O22-, or R-O-O-R). Several different organic chemicals are capable of forming peroxides. Peroxide formation in solvents and reagents has caused many laboratory accidents. Every worker must learn to recognize and safely handle peroxidizable compounds.

Peroxides form by the reaction of a peroxidizable compound with free radicals and molecular oxygen through a process called autooxidation or peroxidation. Peroxidizable compounds are insidious. Under normal storage conditions, they can form and accumulate peroxides, which may explode violently when subjected to thermal or mechanical shock. This can occur even when the containers appear to be tightly closed.

Peroxides in solution do not normally present thermal or shock hazards at concentrations up to about one percent (1%). You can safely dispose such solutions or treat them to remove peroxides. However, if you notice visible crystals in a peroxidizable liquid or discoloration in a peroxidizable solid, peroxide concentrations greater than 1% are likely already present. Such chemicals are extremely dangerous, and might require special handling and disposal procedures. Do not handle chemicals that you suspect might have significant peroxide contamination. Leave the chemicals in place and contact EHS.

Figure 13.1
Following years of uninhibited peroxidation, this bottle of isopropyl ether contains a large chunk of explosive peroxide crystal. A high-hazard removal company took this bottle from the lab and detonated it with a blasting cap, visible on top of the tape. Photo courtesy of Reactive Hazards Reduction, Inc.

To prevent accidents caused by peroxidizable compounds, your laboratory safety procedures should emphasize:

  • Recognition of chemical structures that may form peroxides (Appendix 13-A, Table I)
  • Use of hazard identification labels
  • Controlled inventory of peroxidizable compounds
  • Use of peroxide detection tests and peroxide removal procedures
  • Proper safety equipment and process procedures