Question
How do I identify and handle peroxide forming chemicals?
Answer
Several organic solvents undergo auto-oxidation over time to product unstable peroxides and hydroperoxides. Many of these will be shipped containing a peroxide stabilizer. Those that contain a stabilizer may still undergo auto-oxidation but at a much slower rate. Peroxides can cause serious injury and may even be fatal under certain conditions due to their highly unstable nature. Peroxides can explode violently when subjected to light, heat, friction, or mechanical shock. Peroxides forming chemicals are separated into four different Groups. Chemicals that fall within these groups are listed in the attached Peroxide Forming Chemicals document on this page.
- Group A: Chemicals that form explosive levels of peroxides without concentration. Severe peroxide hazard after prolonged storage, especially after exposure to air. All have been responsible for fatalities. Test for peroxide formation before using or discard after 3 months.
- Group B: Peroxide hazards on concentration. Test for peroxide formation before distillation or evaporation. Test for peroxide formation or discard after 1 year.
- Group C: Chemicals, which are hazardous due to peroxide initiation of auto-polymerization. The peroxide-forming potential increases for liquids of this group, especially for butadiene, chloroprene and tetrafluoroethylene, such that these materials should be considered as a peroxide hazard. Test for peroxide formation or discard liquids after 6 months; discard gases after 1 year.
- Group D: Chemicals that may form peroxides but cannot clearly be placed in Classes A through C.
Safe storage
- Peroxide forming chemicals should be purchased in the minimum volume necessary for the intended application
- Peroxide forming chemicals should be stored according to their hazard classification. E.g. flammables should be stored in a flammable cabinet
- Label each container with date received, date opened, and date tested (if applicable)
- Always perform a peroxide test before doing distillation or purification of peroxide forming chemicals
- Never distill peroxide formers completely dry. Always leave about 20% of chemical in the still
- Wear proper PPE including gloves, safety glasses or goggles, face shield, and a fire-resistant lab coat
- DO NOT use metal spatulas to handle solid peroxides. Ceramic, Teflon, or wooden spatulas may be used if they do not generate a static charge
- Opened peroxide forming chemicals should be tested at least annually to determine if peroxides are present. Testing frequency will depend on the Group of peroxide forming chemical. Test strips can be easily purchased or obtained from USD’s EH&S department
Disposal
- Group A peroxide forming chemicals should be disposed of within 3 months of opening the container. Group B peroxide forming chemicals should be disposed of within 1 year of opening the container. Group C peroxide forming chemicals should be disposed of within 6 months of opening the container. Group C peroxide forming gases should be disposed of within 1 year of opening the container
Stabilization
- Many peroxide forming chemicals can be purchased with <1% stabilizer added into the container
- Upon a positive peroxide test, alert USD EH&S personnel immediately. EH&S will stabilize the container through addition of Xpell-R powder and dispose of the container
- After stabilization with Xpell-R powder the chemical will be unusable
Items of Note
- Peroxide levels assessment:
- < 25 ppm is considered safe for general use
- 25 – 100 ppm is not recommended for distilling or concentrating
- 100 ppm or more is considered dangerous. Avoid handling and contact USD EH&S personnel immediately to arrange disposal
- Many peroxides are shock and heat sensitive. Take great care when handling peroxide forming chemicals
- If you are unsure if a chemical is safe to handle, consult USD EH&S. DO NOT attempt to handle it yourself
- Treat all peroxide forming chemicals older than 1 year as if they contain explosive peroxides until otherwise determined. If a chemical should be a liquid and it is a solid, it is likely not safe to handle
- If you see crystal formation, such as that shown in the following photo, DO NOT handle the container or surrounding containers and alert USD EH&S personnel IMMEDIATELY
