SOP: Peroxide-Formers

Hazard Description

Peroxide-forming chemicals are a class of materials that have the ability to form shock-sensitive and explosive peroxide crystals. When triggered by friction or shock, the peroxides will explode. Peroxide forming chemicals include solids, liquids, and gases. These chemicals may also be flammable or reactive, so other SOPs will likely apply to their use in the laboratory. The safety data sheet and label for peroxide-forming chemicals may or may not include the following hazard statement: 2.3 Hazards not otherwise classified (HNOC) or not covered by GHS: May form explosive peroxides.

Peroxides form after exposure to air. The rate of peroxide formation is dependent on the specific chemical, the amount of air exposure, and whether the chemical contains an inhibitor to retard peroxide formation.

There are three classes (A-C) of potentially peroxide-forming chemicals.  Each of the classes is defined below in the List of Peroxide Forming Chemicals section, along with their storage limitations.

To identify the chemicals with this hazard in your ChemTracker chemical inventory, use the instructions in EHRS Tip Sheet:  Completing a Hazard List Analysis.

Approvals

If you or your lab has not worked with this hazard before and you are considering a procedure that requires you to do so, we recommend contacting EHRS for guidance.

All work that involves the handling or transfer of peroxide-forming chemicals requires the approval of the P.I.  The P.I. must ensure that the person or team who will be working with the chemicals understands the hazards and has received adequate training and supervision for the procedure. 

EHRS approval is required for the purchase of inhibitor-free peroxide-forming solvents and peroxide-forming gases.

For any task that requires safety controls beyond those specified in this SOP, a task-specific Hazard Control Plan (HCP) must be written.  The HCP must be sent to EHRS for review.  EHRS will upload the HCP to the “documents” section of the lab’s BioRAFT page.

Training Requirements

No researcher may work independently with the hazardous material described in this SOP until the Principal Investigator (or their designee) has ensured that the researcher:

• Has completed all required EHRS laboratory safety training programs
• Understands the hazards of the materials and risks of the processes involved
• Has read and understands the contents of this SOP
• Demonstrates the ability to execute their work according to the requirements in this SOP

Facility Requirements

The facility requirements for peroxide-forming chemicals will depend, in part, on the other hazards of the materials, including their toxicity, flammability, and reactivity.  General facility requirements for working with hazardous chemicals include the following:

General Ventilation

Hazardous chemicals may not be handled or stored in a room or facility with recirculating exhaust.

Chemical Fume Hood

All work with hazardous chemicals in open or closed systems must be done in a designated area of a laboratory inside of a properly functioning chemical fume hood.

Emergency Irrigation

Emergency irrigation (safety shower, eyewash) must be accessible within a 10-second travel distance of the area where the work is performed.

Signage and Labeling

A legible manufacturer’s label including hazard information must be present on all commercial containers of peroxide-forming chemicals.

If peroxide-forming chemicals are transferred to another container for storage or to make stock solutions for later use, special labeling requirements apply.  See the “Researcher-Created Labels” section in Section IV:  Chemical Container Labeling in this CHP for a complete list of requirements.

Date Containers

Write on the container label the date that any peroxide-forming material was received and the date the container was opened.  (See Storage and Transport below for information about storage limitations and expiration.)

Storage and Transport

Proper storage and transport of peroxide-forming chemicals must be determined by assessing all of the hazards and physical properties of the chemical. 

See Section VI:  Chemical Storage and Transportation in this CHP for a complete list of requirements.

Specific Storage Requirements for Peroxide-Forming Chemicals

Peroxides form after exposure to air. The rate of peroxide formation is dependent on the specific chemical, the amount of air exposure, and whether the chemical contains an inhibitor to retard peroxide formation.

• Peroxide-forming chemicals must be stored away from light and heat with tightly secured caps.
• Containers must be labeled with dates of receipt and opening.
• Peroxide-forming chemicals must be entered into the lab’s chemical inventory and assigned an expiration date based on the storage limitations for the chemical’s class (see class descriptions below in List of Peroxide-Forming Chemicals).

Hazard Controls

Engineering Controls

Chemical Fume Hood

All work with peroxide-forming chemicals in open or closed systems must be done in a designated area of a laboratory inside of a properly functioning chemical fume hood.

The fume hood is designed to capture chemical vapor and the hood sash acts as a shield in case of chemical splash.  The sash must be kept closed as much as feasible.

Vacuum Protection

Mechanical vacuum pumps must be protected using cold traps and, where appropriate, must include a filter to prevent particulate release.  The pump exhaust must be vented into an approved exhaust duct or chemical fume hood.

Glove Box

Certain peroxide-forming chemicals must be handled in a glove box rather than a fume hood. The Office of Environmental Health and Radiation Safety (215-898-4453) or the Principal Investigator will determine if this is required.

If a chemical fume hood or glove box is not available, contact EHRS to determine whether the risks can be adequately controlled using alternative controls.

Work Practices

A list of recommended work practices for hazardous chemical handling is included in Section V: Chemical Handling in this CHP. Of particular relevance to peroxide-forming chemical use:

Considerations for purchase

• Whenever the presence of the inhibitor will not adversely affect your research results, purchase peroxide-forming chemicals that include an inhibitor to prevent the formation of peroxides.
• Contact EHRS for guidance when it is necessary to purchase inhibitor-free peroxide-forming chemicals.
• Do not use peroxide-forming chemicals if less-hazardous alternatives are possible.
• Purchase, dispense, and use the smallest quantity of peroxide-forming chemicals possible. 
• Purchase the lowest concentration of peroxide-forming chemicals that will meet your research needs.

Considerations for general handling

• Do not handle peroxide-forming chemicals when working alone.
• Immediately close all containers of peroxide-forming chemicals after use.
• Never use peroxide-forming chemicals that have expired or if the date received or opened is unknown.
• Contact EHRS immediately and do not disturb containers if they appear to have peroxide crystals around the cap or solid crystals inside the bottle.

Considerations for drying solvents

• Check peroxide-forming solvents for the presence of peroxides prior to drying.
• Commercially available Grubb’s-type drying systems (solvent-purification columns) are the safest method to use.
• If distillation is used to dry peroxide-forming solvents, add sodium metal to the distillation pot to reduce peroxide formation and add benzophenone as an indicator for the presence of sodium metal. The resultant blue color confirms that sodium is still present. Add more sodium metal to the pot when the blue color disappears. (See the SOP: Water-Reactive Chemicals and your lab’s Hazard Control Plans for more information about the safe handling of sodium metal)
• Both Grubb’s-Type Solvent Drying Systems and drying stills may remove the inhibitors (BHA & BHT), therefore the dried, uninhibited solvent must never be stored in the lab. Use immediately after dispensing from the still or drying column.

Testing for Peroxides

Expired peroxide-forming chemicals may be disposed of via EHRS (see Waste and Decontamination section below for details).  You do not need to test for peroxides prior to giving peroxide-forming chemicals to EHRS for disposal.

There may be times when it is advisable to test for the presence of peroxides, such as when using an inhibitor-free product or prior to drying a potential peroxide-forming solvent.  When testing for peroxides, use the following instructions:

1. Use XploSens PS detection strips to check for peroxides. (http://www.sigmaaldrich.com/catalog/product/aldrich/z683108?lang=en®ion=US).
2. While there are no safe peroxide levels, contact EHRS if solvent test shows peroxides >50ppm.
3. Test all un-inhibited peroxide-forming chemicals before each use. 
4. Contact EHRS immediately and do not disturb containers if they appear to have peroxide crystals around the cap or solid crystals inside the bottle.

Additional work practices for reducing the risks of any lab procedure involving peroxide-forming chemicals must be described in a written Hazard Control Plan.

Personal Protective Equipment

Consider the potential routes of exposure and health consequences when selecting personal protective equipment (PPE) for tasks involving peroxide-forming chemicals. 

In addition to the minimum lab apparel and PPE requirements, other protective equipment may be necessary to reduce risks.  When additional equipment (such as tight-fitting chemical splash goggles, chemical-resistant gloves, or disposable lab coats) are required, a Hazard Control Plan must be written to document the risk assessment and controls.

Contact EHRS for assistance with risk assessments, glove compatibility, and other PPE selection.

The minimum PPE requirements for all chemical handling tasks, and information about specialty PPE can be found in the "Personal Protective Equipment" section of Section V:  Chemical Handling in this CHP.

Waste and Decontamination

Wash hands thoroughly with soap and water after handling any chemical and whenever you leave the lab.

Use good housekeeping practices to avoid contamination of surfaces, garments, personal belongings, and self.

Decontaminate all surfaces that have come in contact with peroxide-forming chemicals and clean-up small spills promptly.  See the chemical Safety Data Sheet or contact EHRS for assistance with determining an appropriate decontamination method.  See “Spills” below for instruction on what to do in the event of a large or hazardous spill of a peroxide-forming chemical.

Peroxide-forming chemicals that contain inhibitor and have not yet expired may be collected for EHRS hazardous waste collection as described in the Laboratory Chemical Waste Management Guidelines.

Contact EHRS immediately to arrange disposal of any container of peroxides that is more than a year past its expiration, has tested positive for >50 ppm of peroxides, is of unknown age, or has any solid/crystal formation on the container, especially around the cap.   Do not attempt to move, open, or otherwise disturb any container that you believe may contain explosive peroxides!  

For complete hazardous waste guidelines, see the waste section of the EHRS website: Laboratory Chemical Waste Management Guidelines

Emergencies

Emergency Contacts

General emergency response information can be found at Emergency Info.

Suspected Peroxide Contamination in or on a Container

Contact EHRS immediately to arrange disposal of any container of peroxides that is:

• More than a year past its expiration
• Has tested positive for >50 ppm of peroxides
• Is of unknown age
• Has any solid/crystal formation on the container, especially around the cap.   

Do not attempt to move, open, or otherwise disturb any container that you believe may contain explosive peroxides!  

Spills

General procedures for chemicals spill response can be found in Section X: Chemical Spills in this CHP.

Do not hesitate to call EHRS for assistance with spill cleanup for peroxide-forming materials.

24 hours: 215-898-4453

Contact Penn Police (511) only if the spill involves a fire, imminent risk of fire, an injury requiring an ambulance, or if there is a hazard that may affect others in the building.

List of Peroxide-Forming Chemicals

This list is provided as a guide of peroxide-forming chemicals commonly found in labs and is not a comprehensive list. 

Classes of Peroxide-Forming Chemicals

Peroxide-formers fall into three classes.

Class A Peroxide-Forming Chemicals

These chemicals can form explosive levels of peroxides while sitting on the shelf. These chemicals should be tested before use or disposed of through the chemical waste system three months after opening or at the expiration date on the container if unopened. Contact EHRS if there crystals are present or if the solvent is discolored.

Expire 3 months after opening

Class B Peroxide-Forming Chemicals

Class B peroxide-formers are only a hazard if the peroxides are concentrated, which may happen upon evaporation or distillation of the solvent. These materials should be disposed of one year after opening or at the expiration date on the container if unopened.

Expire 1 year after opening

Class C Peroxide-Forming Chemicals

Class C peroxide-formers may auto-polymerize as a result of peroxide formation. These materials should be disposed of  one year after opening or at the expiration date on the container if unopened.

Expire 1 year after opening

Related SOPs and Fact Sheets

SOP:  Flammable Liquids

SOP:  Strong Oxidizers

SOP:  Reactive Chemicals

SOP:  Explosive Compounds

SOP:  Water-Reactive Chemicals

References

1. http://www.sigmaaldrich.com/chemistry/solvents/learning-center/peroxide-formation.html#sthash.Rhw4RSHu.dpuf
2. Peroxides and peroxide-forming compounds Chemical Health and Safety, 09/2001, Volume 8, Issue 5, p. 12 (available from Penn Library)
3. Ethyl ether and other peroxide-forming ethers, Chemical Health and Safety, Volume 10, Issue 1, January–February 2003, Pages 42 (available from Penn Library)