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California State University, Long Beach
College of Natural Sciences and Mathematics

Safety Requirements for Peroxide-Forming Materials

Revised July 2019

This policy presents mandatory CNSM safety procedures designed to prevent injury and property damage from peroxide explosion and fire. Some of the materials known to form shock sensitive explosive compounds when in use/storage are listed below.

Please note: the lists below are not all inclusive. CNSM personnel are required to know the hazardous properties of the materials they possess and use. A material's potential for becoming explosive is ONE of the hazards that must be known and addressed through responsible use, storage and disposal. The specifically-referenced materials listed below and all other peroxide-forming chemicals are also typically flammable and toxic. Refer to Safety Data Sheets (SDSs) and other safety references for complete hazard information.

The materials in bold font are known to have been used within the CNSM.

Group A: Common EXTREMELY HAZARDOUS Peroxide Formers

(form explosive levels of peroxides without concentration)

  • isopropyl ether1,2
  • dichloroethylene

Group B: Common Peroxide Formers That Pose a Serious Hazard

(peroxide hazard when concentrated by distillation or evaporation)

  • acetaldehyde diethyl acetal (acetal)1,2
  • acetaldehyde1
  • furan1,2
  • isopropylbenzene (cumene)2
  • cyclohexene1,2
  • dioxane2
  • dicyclopentadiene1,2
  • diacetylene1,2
  • vinyl ethers1,2
  • diethylene glycol dimethyl ether (diglyme)1,2
  • diethyl ether (ether)1,2
  • cyclopentene1,2
  • ethylene glycol dimethyl ether (glyme)2
  • methyl acetylene1,2
  • methyl cyclopentane2
  • methyl-isobutyl ketone1,2
  • tetrahydrofuran (THF)1,2
  • decalin (decahydronaphthalene)1
  • tetralin (tetrahydronaphthalene)2
  • diacetylene (butadiyne)1

1. Possession Restrictions

"GROUP A" materials may not be acquired or used without special permission from the Science Safety Office and Campus Environmental Health & Safety (EH&S). If permission is granted, only the minimum quantity required for a process will be permitted. Any of these materials remaining three months after opening must be surrendered as hazardous waste.

2. Peroxide Minimization

Whenever possible, Group A and Group B materials must be acquired in the "inhibited" form – containing additives that slow peroxide formation. Peroxide formation requires oxygen. Since air contains oxygen, these materials should be stored under nitrogen or in some other oxygen-free environment. The rate of peroxide formation is increased when the material is anhydrous and/or exposed to light. Add some water when possible and always store these materials in metal cans or brown bottles with plastic caps. Storage in clear glass containers is prohibited. Storage in containers with metal caps or ground glass stoppers/fittings is prohibited; they can generate dangerous friction when opened, and initiate a peroxide explosion.

3. Storage Limits and Mandatory Disposal

Discarding these materials before an unsafe level of peroxide can form is the best way to avoid peroxide dangers and unnecessarily high disposal costs. EH&S requires that CNSM faculty and staff carefully monitor the age of any peroxide forming materials in their possession. Each container of peroxide-forming material must be dated when received and when first opened; these dates determine disposal timelines. The basic storage durations/disposal dates are as follows:

  • Group A – 3 Months from date first opened. If never opened, discard after one year.
  • Group B – 12 Months from date first opened. If never opened, discard after 5 years.

Storage of Group B materials may continue as long as they are tested every 6 months after the first year, peroxide content is less than 100 ppm and each date of testing is clearly written on the container. Peroxide-formers dispensed from solvent dispensers must be tested 12 months from the date dispensed then every 6 months thereafter. CNSM Safety provides bottle labels on which to write critical dates and testing results. Group B peroxidizable materials still in use 12 months from the date first opened may NOT be distilled without current peroxide test results which show the presence of less than 100 ppm peroxide.

4. Peroxide Testing Guidelines

Various chemical companies make "dip" strips for the semi-quantitative detection of peroxides in organic and inorganic solutions, and they are available from many suppliers. The indicator on the strip turns blue in the presence of peroxides. Comparison color scales are provided for organic and aqueous tests. Organic solutions generally require slightly different testing procedures than aqueous solutions. When using test strips, the following guidelines must be followed;

  1. Thoroughly read and follow all manufacturer's instructions for the particular type of solution (organic or aqueous) to be tested.
  2. Carefully inspect the container PRIOR to opening it. Contact the Science Safety Office immediately upon discovery of containers containing visible crystals, visible precipitate or an oily viscous layer present in the material. Do not attempt to move or open any container in this state.
  3. Determine when the container was received, first opened or last tested. These dates should be clearly written on the Science Safety Office provided container label. If this information cannot be determined, Contact the Science Safety Office for further evaluation. Do not attempt to open the container.
  4. Following testing, clearly write the date tested and results (in ppm) on the container label.

The Science Safety Office and Chem Issue have peroxide test strips. Contact the Science Safety Office for assistance with testing. Prior to testing, always closely examine the container for the presence of crystals. Crystals formed near a container's cap can lead to a particularly dangerous situation. The Science Safety Office sends out testing reminders via email every six months.

Old, neglected containers of peroxide forming materials that have been left undisturbed beyond their testing intervals may be unsafe to open for testing and may require disposal as the only safe means of dealing with them. Campus EH&S may hold departments or individuals financially responsible for disposal charges in cases of neglect.

5. Training

In person training provided by the Science Safety Office is required to be completed by anyone that will work with or perform testing of peroxidixable materials. Trained research PIs or area supervisors may provide this training to their personnel if it is documented and at minimum covers the material presented in this policy.

Please contact the Science Safety Office at 5-5623 (off campus call 562.985.5623) for disposal of outdated peroxide-forming materials, training or for clarification of this policy.


1Sigma-Aldrich Featured Article on Peroxide Forming Solvents (available at

2Prudent Practices in the Laboratory: Handling and Management of Chemical Hazards, Updated Version. 2011. The National Academy of Sciences