LBNL Time-Sensitive Chemicals Overview

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.

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

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)

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)

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