7.5 Peroxide-Forming Chemicals and Highly Reactive Substances

Peroxide Forming Chemicals

Peroxide-forming chemicals (PFCs) are chemicals that can “auto-oxidize” with atmospheric oxygen under ambient conditions to form organic peroxides (contains an -O–O- bond). Peroxide formation can be initiated by exposure to air, self-polymerization, or solvent impurities. Once formed, organic peroxides are sensitive to thermal or mechanical shock and can be violently explosive in concentrated solutions or as solids.

Many common organic laboratory solvents, such as ethers or tetrahydrofuran, can form peroxides if not stored or used appropriately. A larger list of chemicals, including common laboratory chemicals such as isopropyl alcohol, can also form peroxides if best practices are not followed.

UMN maintains an extensive list of peroxide forming chemicals with references that include any peroxide formation data and incidents reported for those compounds. Lists can also be found in Prudent Practices and from chemical manufacturers.

Instructions for Researchers:

  • Review the Peroxide-Forming Chemicals Guidance Document.
  • Check your lab for PFCs. Even seemingly stable solvents may form peroxides in certain circumstances.
  • Inventory the chemicals in your lab using Chematix, which can be used to run reports for PFCs.
  • Inspect all chemical bottles for signs of decomposition (e.g. solvent discoloration, crystal or solid formation, bottle/cap/label degradation, etc.). Do not open suspect containers and contact the HSRM Regulated Waste Program at (612) 626-1604 for disposal assistance.
  • Label all PFCs with the following information:
    • Date received
    • Date opened
    • Discard by date
    • Peroxide test date (if open) and results
  • Routinely test peroxide forming solvents and adhere to disposal recommendations.
  • Close out labs in a timely manner and discard PFC’s rather than saving them or donating them to other laboratories. Never donate chemicals that are past their expiration dates or where quality is questionable.

Peroxide Testing and Disposal Requirements

You are not required to test for peroxides if you are not comfortable doing so, simply state in your disposal request that the solvent has not been tested and note the approximate age of the bottle. The testing and disposal requirements for PFCs depend on the class designation (Class A-D), which are based on the time it takes to form explosive levels of peroxides. Below is a description of the classes along with testing and disposal requirements.

Class A: Chemicals that form explosive levels of peroxides without concentration, even when unopened.

  • Test for peroxides before high-hazard procedures
  • Dispose of within 3 months of receipt

Example: Isopropyl ether, Tetrahydrofuran without inhibitor

Class B: Chemicals that are a peroxide hazard when concentrated through evaporation or distillation.

  • Test for peroxides before high-hazard procedures and every 6 months after opening
  • Dispose of by their expiration date or within 2 years of receipt

Example: Tetrahydrofuran with inhibitor, vinyl ethers, and secondary alcohols

Class C: Chemicals that may autopolymerize without an inhibitor.

  • Test for peroxides before high-hazard procedures and every 6 months after opening
  • Dispose of by their expiration date or within 2 years of receipt

Example: Acrylic Acid, Methyl methacrylate

Class D: Additional chemicals that may form peroxides.

  • Best practice to test before high-hazard procedures or within 2 years of receipt
  • Dispose of by the expiration date or within 2 years of receipt unless the chemical quality is confirmed

Use the chart below to determine appropriate action based on peroxide test results:

Peroxide Concentration


Under 20 ppm The solvent is safe for use
Between 20 and 100 ppm The solvent should not be distilled or concentrated
Between 100 ppm and 400 ppm The solvent must be disposed of as waste
Above 400 ppm Immediate HSRM assistance and evaluation is needed

All PFCs with peroxide concentrations > 100 ppm must be disposed of using the online Chemical Waste Disposal Procedures.

  • Indicate the peroxide concentration in the comments section of the online request
  • Do not mix peroxide containing solvents with other waste streams
  • Add a dash of additional inhibitor prior to disposal, if you have it

PFCs with peroxide concentrations > 400 ppm must be evaluated by HSRM to determine the safest method for disposal. Do not move the container and contact HSRM Regulated Waste Program at (612) 626-1604.

Contact the Regulated Waste Program Immediately

  • If crystals are visible on or in the container or lid
  • If the container has a metal screw cap or glass stopper
  • If a Class A compound is past its expiration date 
  • If a Class B or Class C compound has been open for more than 1 year and has not been tested

Do NOT open or move the container. Contact the Regulated Waste Program at (612) 626-1604 for assistance.

UMN Resources

Consultations and hazard assessments can be performed with the Research Safety Professional assigned to your area or contact the Health, Safety, and Risk Management main office at (612) 626-6002 or [email protected].


If you do not have access to one of these resources, contact your Research Safety Professional for more information.