Time-sensitive chemicals are chemicals that can develop additional hazards over time, on top of their initial hazards, even if stored and handled properly.
Routine use of time-sensitive chemicals at LBNL relies on effective strategies to ensure these chemicals remain safe to handle over their entire lifecycle. Our time-sensitive chemical program has requirements for chemical owners, activity leads, and workers using peroxide-forming chemicals and other classes of time-sensitive chemicals.
A high-level overview of time-sensitive chemicals at LBNL is provided here, as well as links to additional resources. EHS is available to provide consultation. Email chemsafety@lbl.gov for assistance.
Classification and Hazards
There are five different types of time-sensitive chemicals at LBNL. Each type has specific hazards and warning signs. If any of the warning signs below are observed, do not disturb the container. Contact your DSC and H&S Rep immediately for assistance.
Peroxide-Forming Chemicals
Common Examples: Many ethers, such as diethyl ether and tetrahydrofuran; some alcohols such as 2-butanol; some alkenes such as cyclohexene and 1-pentene; some monomers such as methyl methacrylate and styrene; and some inorganic chemicals such as potassium metal and sodium or potassium amide.
Hazard Description: May form explosive peroxides
Key Warning Signs: Visible peroxide crystal formation, precipitation, layering, clouding, or discoloration
Peroxide forming chemicals are further broken down into groups A, B, and C.
Group A peroxide forming chemicals are the most dangerous – they have the ability to build up peroxides in high concentrations that are potentially explosive.
Group B peroxide forming chemicals build up peroxides in lower concentrations, so that the mixture is only explosive if the peroxides are concentrated through evaporation, distillation, or other means of removing the non-peroxidized solvent.
Group C peroxide forming chemicals are very similar to Group B, but also have the ability to polymerize exothermically and violently if the peroxides are allowed to accumulate.
Unstable/Self-Reactive Chemicals
Common Examples: Hydrogen peroxide ( ≥ 30%), formic acid ( ≥ 98%), benzyl halides, chloroformates
Hazard Description: May rupture container
Key Warning Signs: Bulging cap or container, discoloration, or improper storage for extended periods of time
Explosive When Dry Chemicals
Common Examples: Highly nitrated substances such as picric acid and 2,4-Dinitrophenylhydrazine; many azides, azo and diazo compounds such as ethyl diazoacetate and benzenesulfonylazide; some other compounds with high nitrogen content such as 1-H tetrazole and N-Methyl-N’-nitro-N-nitrosoguanidine.
Hazard Description: Explosive when dry
Key Warning Signs: Visually dry contents, dry residue around or under the cap or on the outside of the container, or solid material has precipitated from solution (in cases where the material is soluble in its stabilizing liquid)
Time-Sensitive Gases
Common Examples: hydrogen bromide gas, hydrogen fluoride gas
Hazard Description: May rupture cylinder
Key Warning Signs: Expired material (default shelf life or manufacturer’s expiration date), signs of corrosion or damage to the cylinder, especially near welding or valves, including frozen or stuck valves or blockages in the valve or regulator, or increase in pressure (if already connected to a regulator)
Chemicals that May Undergo Hazardous Polymerization
Common Examples: 2-furaldehyde, ethyl acrylate, butyl isocyanate, methacrolein
Hazard Description: May violently polymerize
NOTE: Requirements apply to > 4 L or 4 kg containers ONLY. Some chemicals in this class form peroxides that may initiate explosive polymerization.
Key Warning Signs: Suspected peroxide formation or depletion of inhibitor, thermal shock, contamination, damaged/distorted container, or expired material
Management
Each hazard class of time-sensitive chemicals has specific labeling, inspection criteria, and additional requirements. Those managing time-sensitive chemicals must have sufficient training and work authorization. Refer to links for more detailed information on requirements for properly managing specific types of time-sensitive chemicals.
Inspection Frequency of Time-Sensitive Chemicals
| Warning Label Required | Time-Sensitive Chemical Type | Inspection/Test Frequency After Opening | Maximum Storage Time1 |
|---|---|---|---|
| May form Explosive Peroxides | Peroxide Former Group A | 3 months | 18 months, if unopened2 |
| Peroxide Former Group B | 12 months | ||
| Peroxide Former Group C | 12 months(24 hours if uninhibited) | ||
| Inorganic Peroxide Former:Potassium Metal | 12 months | 5 years from date of receipt, if under oil in ambient conditions3 | |
| Inorganic Peroxide Former:Sodium/Potassium Amide | 3 months | 3 months from date of receipt | |
| May Rupture Container | Unstable/Self-Reactive with Production of Gaseous Products | Not greater than 12 months | Manufacturer’s expiration date, if provided |
| Explosive When Dry | Explosive When Dry | Not greater than 12 months | Manufacturer’s expiration date, if provided |
| May Rupture Cylinder | Time-Sensitive Gas | Not greater than 6 Months | Default shelf life applies, if none provided by manufacturer |
| May Polymerize Violently | Hazardous Polymerization (Container >4L or 4kg ONLY) | Not greater than 12 months | Manufacturer’s expiration date, if provided |
- Make arrangements to properly dispose of the chemical before the maximum storage time is exceeded. For Peroxide Formers A/B/C only: If the chemical is still needed, it must be opened and tested for peroxides when the maximum storage time is met. If the peroxide concentration is within acceptable limits, the chemical can be kept for use with continued inspection/testing.
- This maximum storage time is currently recommended as a requirement for Group B and best practice for Group A/C.
- Potassium stored under vacuum or an inert atmosphere does not have a maximum storage time.
Time-Sensitive Chemical Resources
- Request Time-Sensitive Chemical Labels
- Request Peroxide Test Strips
- Peroxide Testing Video Tutorial
- Current list of LBNL Peroxide-Forming Chemicals
- Current list of Time-Sensitive Chemicals
- Current list of Peroxide-Forming Chemicals requiring testing prior to disposal
- Peroxidizable and Polymerizable Compound Evaluation Form (sometimes required by Waste Management for requisition of peroxide-forming chemicals)
