Abstract: Tamper-respondent assemblies are provided which include individualized fluid chemical mixtures for tamper detection. The tamper-respondent assemblies include, for instance, a circuit board and an enclosure. The circuit board includes an electronic component, and the enclosure is mounted to the circuit board to enclose the electronic component within a secure volume, where the secure volume is a sealed space. A fluid is disposed within the secure volume that includes a chemical mixture of multiple chemical substances, and the multiple chemical substances have randomly generated concentrations within the chemical mixture. One or more sensors are provided to facilitate detecting a change in the chemical mixture of the fluid within the secure volume indicative of a tamper event.