Peroxide-Forming Chemicals Policy


It is the policy of the University of Nevada, Reno to use, store, and dispose of peroxide-forming chemicals in a manner that will minimize risks to personnel, university facilities, and the environment.


Vice President for Research; Environmental Health and Safety Department


This policy applies to all teaching and research laboratories, and chemical stockrooms and storerooms maintained by University of Nevada, Reno.


Ethers and many other organic chemicals can undergo autooxidation in the presence of oxygen and form peroxides during storage. The peroxides formed are sensitive to shock, heat, or friction to varying degrees. Additionally, alkali metals and their amides can form a peroxide or superoxide surface layer that is shock sensitive. If you possess any of the following chemicals, you must evaluate them and implement a continuous surveillance schedule as described in this document.

Potential Peroxide-Forming Chemicals (not all inclusive)

List A

These chemicals form explosive levels of peroxides without concentration. Discard or test for peroxides every 3 months after open date.
Chemical Name CAS Number
Divinyl acetylene 821-08-9
Potassium metal 7440-09-7
Sodium amide 7782-92-5
Diisopropyl ether 108-20-3
Potassium amide 17242-52-3
Vinylidene chloride 75-35-4

List B

These chemicals produce some peroxides when stored; there is increased risk when concentration occurs. Do not distill or evaporate without first testing for the presence of peroxides. Discard or test for peroxides at least every 12 months after open date. Some of these chemicals (e.g. some secondary alcohols) may form peroxides more slowly than others, but all should be treated as List B peroxide formers.
Chemical Name CAS Number
Acetaldehyde 75-07-0
Benzyl alcohol 100-51-6
2-Butanol 78-92-2
Cumene 98-82-8
Cyclohexanol 108-93-0
2-Cyclohexen-1-ol 822-67-3
Cyclohexene 110-83-8
Cyclooctene 931-88-4
Cyclopentene 142-29-0
Decahydronaphthalene 91-17-8
Diacetylene 460-12-8
Dicyclopentadiene 77-73-6
1,1-Diethoxyethane (acetal) 105-57-7
Diethyl ether 60-29-7
1,4-Dioxane 123-91-1
Diethylene glycol dimethyl ether (diglyme) 111-96-6
Ethylene glycol dimethyl ether (glyme) 110-71-4
Furan 110-00-9
4-Heptanol 589-55-9
2-Hexanol 626-93-7
Methylacetylene 74-99-7
3-Methyl-1-butanol 123-51-3
Methylcyclopentane 96-37-7
Methyl isobutyl ketone 108-10-1
4-Methyl-2-pentanol 108-11-2
2-Pentanol 6032-29-7
4-Penten-1-ol 821-09-0
1-Phenylethanol 98-85-1
2-Phenylethanol 60-12-8
2-Propanol 67-63-0
Tetrahydrofuran 109-99-9
Tetrahydronaphthalene 119-64-2
Dioxanes N/A
Other secondary alcohols N/A
Vinyl ethers N/A

List C

These chemicals form peroxides which initiate rapid polymerization. Uninhibited chemicals are not to be stored longer than 24 hours.

Liquids at Room Temperature and Pressure – Discard or test for peroxides within 12 months after open date.
Chemical Name CAS Number
2-Chloro-1,3,Butadiene (Chloroprene) 126-99-8
Styrene 100-42-5
Vinyl acetate 108-05-4
Vinyl pyridine 1337-81-1
Gases at Room Temperature and Pressure – If transferred to a secondary container, discard within 12 months after transfer date.
Chemical Name CAS Number
Butadiene 106-99-0
Chlorotrifluoroethylene 79-38-9
Tetrafluoroethylene 116-14-3
Vinyl acetylene 689-97-4
Vinyl chloride 75-01-4

Applicable Regulations

29 CFR 1910.1450, OSHA Standard, Occupational Exposure to Hazardous Chemicals in Laboratories


Deans, Department Chairs, and Directors

Ensure that all principal investigators and laboratory supervisors are aware of the responsibilities and procedures contained in this policy, provide administrative support, and ensure compliance.

Environmental Health and Safety (EH&S)

Provide guidance and assistance in the evaluation and opening of outdated peroxide-forming chemicals (upon request), as well as guidance on safe storage, use, and disposal.

On a case-by-case basis, make the final determination as to whether containers of peroxide-forming chemicals are safe to open by University personnel.

Supply ear plugs and heavy gloves (work gloves) to laboratory personnel for use when opening outdated containers of peroxide-forming chemicals, and provide laboratory personnel assistance in locating a blast shield (all upon request).

Coordinate the disposal of high risk peroxide-forming chemicals by private contractor or other appropriate groups.

On a case-by-case basis, make the final determination as to whether a peroxide-forming chemical that contains between 30 ppm and 800 ppm peroxides can be diluted with a miscible waste chemical or chemical solvent to less than 30 ppm peroxides for disposal through EH&S.

Pick up from laboratories, and dispose of using standard chemical waste disposal procedures, peroxide-forming chemicals that are documented by testing to contain less than 30 ppm peroxides.

Laboratory Principal Investigators and Supervisors

Ensure that laboratory personnel under their supervision are aware of the responsibilities and procedures contained in this policy, and that this policy is implemented as applicable.

Supply peroxide test strips or materials for other accepted (published) quantitative peroxide test methods.

Supply personal protective equipment specified in this document for opening and testing outdated peroxide-forming chemicals. EH&S will supply ear plugs and heavy work gloves upon request.

Supply blast shield (as needed) for personnel when opening outdated peroxide-forming chemicals. EH&S will provide assistance in locating a blast shield on campus that can be borrowed.

Laboratory Personnel

Store, use, and test peroxide-forming chemicals as specified in this document.


Evaluation of Peroxide-Forming Chemicals

Peroxide-forming liquid chemicals which have not been tested for peroxides within the listed time periods must be evaluated as follows:

  1. Visual Inspection

    Visually inspect all peroxide-forming chemicals before any further evaluation. Containers that exhibit any unusual visual characteristics, such as the examples listed below, should be assumed to contain dangerous levels of peroxides and should not be disturbed (notify EH&S). EH&S will assist in the evaluation of chemicals. If there is any doubt about the safety of handling a chemical container, notify EH&S immediately.

    Liquid Chemicals:

    • Crystallization (around the cap or in the liquid)
    • Visible discoloration
    • Liquid stratification

    Note: A flashlight or other light source can be used to increase the visibility of the interior of amber bottles.

    Diethyl ether is commonly sold in steel containers which prevents visual inspection of the liquid. Therefore, diethyl ether containers whose age and use history are unknown should be assumed to contain dangerous levels of peroxides, and should not be disturbed.

    Solid Chemicals (potassium metal, potassium and sodium amide):

    • Discoloration and/or formation of a surface crust (for example, potassium metal forms a yellow or orange superoxide at the surface)

    Note: Evaluation of alkali metals and their amides is based on visual criteria only. These substances react strongly with water and oxygen, and standard peroxide tests should not be used.

    Materials meeting the above criteria are considered to be high risk and will have to be disposed of by special means (limit handling and movement; notify EH&S). Only chemicals which pass visual inspection should be evaluated further.

  2. Opening Container

    Only chemicals that meet the following criteria should be opened and tested for peroxides. Chemicals that do not meet one or more of these criteria should be considered to be high risk, and should not be disturbed (limit handling and movement; notify EH&S).

    • The identity of the chemical is known.
    • The age of the chemical (since manufacture) is known.
    • Evaporation of the chemical is thought to be less than 10% - if this is in question, assume that evaporation has occurred and that high peroxide levels may be present.

    Note: Never try to force open a rusted or stuck cap on a container of a peroxide-forming chemical.

    Additionally, the following classification-specific criteria must be met:

    List A Chemicals

    • Previously opened chemicals not used in the preceding 3 months must be less than 6 months old.
    • Chemicals unopened from the manufacturer must be less than 2 years old.
      • If this is in question, assume the container has been opened.

    List B and List C (liquids) Chemicals

    • Opened chemicals not used in the preceding 12 months must be less than 5 years old.
    • Chemicals unopened from the manufacturer must be less than 10 years old.
      • If this is in question, assume the container has been opened.

    Chemicals not meeting the minimum criteria for opening and testing will be considered to be high risk and must be disposed of by special means (limit handling and movement; notify EH&S). If after opening the container, visual irregularities such as those listed in section 1. are apparent, assume that dangerous levels of peroxides are present. Gently cover the container to minimize evaporation, limit handling and movement, and notify EH&S as soon as possible.

    Safety Precautions:

    Personnel handling containers of outdated peroxide-forming chemicals must wear chemical goggles and a face shield, heavy gloves, and a buttoned lab coat. Hearing protection (plugs or muffs) and a rubber apron are also recommended. Suspect chemical containers must be transferred, one at a time, to a clean (no other chemicals) lab hood. A blast shield must be used when opening or manipulating containers, and testing peroxide levels. Never attempt to force open a stuck cap on a container. Secondary containment for the chemical should also be utilized if practical. Tongs or other forms of remote handling should be used as much as practical. Verify that an operable safety shower/eyewash and fire extinguisher is readily accessible. At least one other person not directly involved in handling of the chemicals should be present.

  3. Peroxide Testing

    For chemicals that have been determined to be safe to open, measure the peroxide concentration using commercial peroxide test strips. Wet chemical detection methods are also available; however, the test strips are gentler, easier, faster, and have greater sensitivity and accuracy, and therefore are recommended for most applications. Laboratory personnel are responsible for performing peroxide testing of chemicals present in their laboratories or storage areas.

    • EM Quant Peroxide test strips manufactured by EM Science (E. Merck) are available from many suppliers (such as Fisher Scientific, Lab Safety and VWR).
      • Chemicals that contain peroxide levels that exceed the test strip detection range may be diluted with a miscible, peroxide-free, solvent.
  4. Dispose of chemical or decontaminate peroxides

    Chemicals with a peroxide concentration of less than 30 ppm can be disposed of through EH&S. Laboratory personnel are responsible for decontaminating chemicals that contain greater than 30 ppm peroxides prior to disposal.

    • Chemicals with a peroxide concentration greater than 800 ppm are considered high risk, and require disposal by special means (limit handling and movement; notify EH&S).
    • Chemicals with a peroxide concentration greater than 100 ppm must be disposed of, or if the peroxide level in a specific container of a chemical on list B is less than 800 ppm, that chemical can be decontaminated and maintained for future use upon the approval of the responsible principal investigator or laboratory supervisor.
      • Peroxides can be removed by chemical methods or column separation (1, 2).
    • Chemicals with a peroxide concentration less than 800 ppm must be decontaminated to reduce the peroxide concentration to less than 30 ppm before disposal (verify treatment with testing). Notify EH&S of treatment and subsequent peroxide concentration when submitting request for waste removal.

    Preparation of Peroxide Formers for Disposal:

    Water-insoluble peroxide formers (ethers, hydrocarbons, etc.) can be decontaminated by shaking with a concentrated ferrous salt solution (5). A solution of 6 g of ferrous sulfate (FeSO4  7H2O), 6 ml of concentrated sulfuric acid, and 11 ml of water is mixed with 1 L of the peroxide former until the peroxide concentration is reduced to below 30 ppm. Reduction of the peroxides generally takes only a few minutes. Re-test the peroxide former after decontamination to verify that the peroxide concentration is less than 30 ppm. Dispose of the decontaminated peroxide former as soon as possible through EH&S (report final peroxide concentration). An alumina column is used as the standard procedure to decontaminate water-soluble peroxide formers (1, 2). Contact EH&S for guidance on decontamination of these chemicals. In some instances it may be permissible to dilute the peroxide concentration to below 30 ppm by mixing the peroxide former with a chemically compatible chemical waste stream or chemical solvent. Contact EH&S prior to diluting any peroxide former in preparation for disposal. After diluting the peroxide former, verify that the peroxide concentration of the resulting mixture is less than 30 ppm, and then dispose of the waste mixture through EH&S (report final peroxide concentration).

  5. Safe Storage and Use of Peroxide-Forming Chemicals

    Maintenance of peroxide-forming chemicals requires implementation of the following procedures:

    1. Identify potential peroxide-forming chemicals (see list on page 1). Prudent practice dictates that laboratories minimize their inventory of peroxide-forming chemicals.
    2. Label each container with the date it is received and the date it is opened.
    3. Store peroxide-forming chemicals in tightly sealed containers to minimize introduction of air. An inert gas such as nitrogen or argon can be introduced into the container as an inert blanket to minimize available oxygen (inhibited vinyl monomers, List C chemicals, are the exception to this recommendation).
    4. Ultraviolet light can initiate autooxidation; therefore, it is best to store peroxide-forming chemicals in containers that exclude light.
    5. Test for peroxides at least as often as recommended in the example lists. Unopened chemicals from the manufacturer must be tested upon reaching the manufacturer’s expiration date, or 18 months, whichever comes first. Chemicals with a peroxide concentration of greater than 100 ppm must be decontaminated or disposed of through EH&S after treatment to reduce peroxides to less than 30 ppm.
    6. Inspect containers of peroxide-forming chemicals frequently, looking for signs of precipitation, stratification of liquid, crystal formation, or other irregularities. The presence of any of these signs indicates a potential shock sensitive container – do not move the container and contact EH&S as soon as possible.
    7. Test for peroxides prior to distilling peroxide-forming chemicals (or prior to other concentration procedures), as this is when explosions commonly occur. It is recommended that 10 to 20% residual bottoms be left during distillation. Additionally, a non-volatile organic liquid, such as mineral oil, can be added to minimize concentration of any peroxides.
    8. Chemical manufacturers often add trace quantities of free radical scavengers (for example, 100 ppm hydroquinone) to inhibit the formation of peroxides. These inhibitors become depleted as peroxides are formed. Additionally, distillation separates the inhibitor from the peroxide-forming chemical. Distilled chemicals and chemicals retained for extended periods should be checked for inhibitor concentration, and inhibitor added if the concentration is below the manufacturer’s specifications (contact the manufacturer for recommendations).


  1. Kelly, R. J. Chem. Health Saf. 1996, 3(5), 28-36
  2. Jackson, H. L.; McCormack, W. B.; Rondestvedt, C. S.; Smeltz, K. C.; Viele, I. E. J. Chem. Educ. 1970, 47(3), A175-88
  3. Clark, D. E. Chem. Health Saf. 2001, 8(5), 12-21
  4. National Safety Council, Recognition and Handling of Peroxidizable Compounds, 1987, Data Sheet I-655-Rev. 87
  5. National Research Council, Prudent Practices in the Laboratory: Handling and Disposal of Chemicals; National Academy Press: Washington, D. C., 1995; pp. 162-163.

Copies of references are available from EH&S.

Related Documents

University Chemical Hygiene Plan