Peroxide-Forming Chemicals

Peroxide forming chemicals (peroxide formers) have the ability to oxidize with atmospheric oxygen under ambient conditions to form shock-sensitive, explosive peroxide crystals. Peroxide formation can be created by exposure to air, self-polymerization, or solvent impurities.

EHS provides labels to help labs manage their peroxide forming chemicals. Please contact ehsaudits@umaryland.edu to request labels.

Safe Handling

Before using a known peroxide former, verify:

  • The identity of chemical. If you are unsure if a chemical is a peroxide former, look at the SDS. Section 2, 7, or 10 will provide information on the chemical’s ability to form peroxides. 
  • That the date last opened (or if unopened, date received) is known and that it is within the recommended safe storage period (see classes below).  
  • That the evaporation of the chemical is known or estimated to be less than 10%. 
  • That the container shows no visible discoloration, liquid stratification, or crystallization (around the cap or in solution).

Crystallization, discoloration, and stratification are signs that a peroxide former may have become shock sensitive. 

Storage

To minimize the opportunity for explosive peroxides to form in chemical storage, please follow these recommendations for best practices:

  • Purchase chemicals in small quantities/ only quantities needed for experiments.  
  • If possible, purchase peroxide forming chemicals containing an inhibitor such as butylated hydroxytoluene (BHT). 
  • Date containers upon receipt and date containers when first opened. 
  • Dispose of containers when expired. Chemical pickup requests can be submitted here. 
  • Store peroxide-formers in airtight bottles, away from light and heat. Avoid using containers with loose-fitting lids and ground glass stoppers. 
  • Do not open any container with evidence of peroxide formation such as obvious crystal formation around the lid or in the liquid, or visible discoloration. 
  • Keep peroxide forming chemicals in their original containers to minimize conditions that accelerate peroxide formation. 

Classes of Peroxide Formers

    Class A Chemicals that form explosive levels of peroxides without concentration. These are the most hazardous and can form explosive peroxide levels even if not opened.   
    Submit a Hazardous Chemical Waste pickup request after 3 months of receiving the chemicals. Do not open container if suspected (e.g., from visual evidence) or known to contain peroxides.      		 Examples: Sodium amide, isopropyl ether  
     
    Click here to see more examples of Class A Peroxide formers.  
    Class B Chemicals that form explosive levels of peroxides after concentration.   
    Inspect for peroxide formation monthly after opening and submit a Hazardous Chemical Waste pickup request after 12 months.   

    Examples: 2-propanol, tetrahydrofuran 

    Click here to see more examples of Class B Peroxide formers. 
    Class C Chemicals that may autopolymerize as a result of peroxide formation. These materials are typically stored with polymerization inhibitors to prevent the polymerization reactions.   
    For inhibited chemicals: Inspect for peroxide formation after opening and submit a Hazardous Chemical Waste pickup request if peroxides are present after 12 months. Uninhibited chemicals should be disposed after 24 hours. Do not store inhibited chemicals under inert atmosphere.  

    Examples: Acrylic acid, methyl methacrylate 

    Click here to see more examples of Class C Peroxide formers. 
    Class D Chemicals that may form peroxides but cannot be clearly placed in Class A-C.  Submit a Hazardous Chemical Waste pickup request after 12 months.  Examples: Isobutyl alcohol, 1-Butanol  
     
    Click here to see more examples of Class D Peroxide formers. 

    Common Peroxide Formers Found in Labs

    1. 2-propanol (Isopropanol) (CAS # 67-63-0) - Class B
    2. Isoamyl alcohol (CAS # 123-51-3) - Class B
    3. Benzyl alcohol (CAS # 100-51-6) - Class B
    4. 2-Butanol (CAS #78-92-2) -Class B
    5. Ethers (e.g. Diethyl Ether; CAS # 60-29-7) - Class B
    6. Cyclohexene (CAS # 110-83-8) - Class B
    7. Tetrahydrofuran (CAS # 109-99-9) - Class B
    8. Acrylic acid (CAS # 79-10-7) - Class C
    9. Acetaldehyde (CAS # 75-07-0) - Class B
    10. Dioxane (CAS # 123-91-1) - Class B