Peroxide forming chemicals are divided into four classes (A-D) which all have different testing and disposal requirements. A list of peroxide formers can be found in here.

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

• Test for peroxides before all procedures and dispose within 3 months of receipt.
  • Ex: isopropyl ether, tetrahydrofuran (without inhibitor)

Class B: Chemicals that form peroxides when concentrated via evaporation or distillation.

• Test for peroxides before high-hazard procedures and every 6 months after opening
• Dispose of by the expiration date or within 2 years of receipt
  • Ex: secondary alcohols, vinyl ethers, tetrahydrofuran (with inhibitor)

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 the expiration date or within 2 years of receipt
  • Methyl methacrylate, acrylic acid

Class D: Chemicals that may form peroxides and do not fall within A-C

• Test before high-hazard procedures or within 2 years of receipt

Handling and Storage Guidelines for Peroxide Formers

The following guidelines should be adhered to when using peroxide forming chemicals:

• Always date peroxide forming compounds upon receipt, upon opening, and the expiration date. Include testing date if the opened bottle has been tested for peroxides.
• Due to sunlight's ability to promote formation of peroxides, all peroxide forming compounds should be stored in an amber bottle and away from heat and sunlight.
• As with any hazardous chemical, but particularly with peroxide forming chemicals, the amount of chemical purchased and stored should be kept to an absolute minimum. Only order the amount of chemical needed for the immediate experiment.
• Never store opened peroxide formers in a refrigerator or freezer.
• Ensure containers of peroxide forming chemicals are tightly sealed after each use and consider adding a blanket of an inert gas, such as N₂, to the container to help slow peroxide formation.
• A number of peroxide forming chemicals can be purchased with inhibitors added. Unless absolutely necessary for the research, labs should never purchase uninhibited peroxide formers.
• Before distilling any peroxide forming chemicals, always test the chemical first with peroxide test strips to ensure there are no peroxides present. Never distill peroxide forming chemicals to dryness. Leave at least 10-20% still bottoms to help prevent possible explosions.
• Certain peroxide-forming chemicals such as diisopropyl ether, divinyl acetylene, sodium amide, and vinylidene chloride must be properly disposed of if they are older than three months. Contact RMS at 940-565-2109 for further instruction if you need to dispose of these substances.
• Chemicals such as dioxane, diethyl ether, and tetrahydrofuran must be properly disposed of after one year if opened or expired. Contact RMS at 940-565-2109 for further instruction if you need to dispose of these substances.

While no definitive amount of peroxide concentration is given in the literature, a concentration of 50 ppm should be considered dangerous and a concentration of >100 ppm should be disposed of immediately. In both cases, procedures should be followed for removing peroxides formers and should be disposed of as hazardous waste.