Time-sensitive chemicals are substances that can become significantly more hazardous as they age due to peroxide formation, decomposition, polymerization, container pressurization, or increased sensitivity to shock and friction. Examples include peroxide-forming solvents, picric acid, chloroform, alkali metals, and certain compressed gases.
Laboratory personnel who use or store these materials must follow the USD Guide for Time-Sensitive Chemicals and ensure that containers are properly labeled, regularly inspected, tested when required, and disposed of before exceeding recommended storage periods. Proper management of time-sensitive chemicals helps prevent fires, explosions, toxic releases, and other serious laboratory incidents.