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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. . 

• 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

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