Chemical indicators (Cis) are almost always irreversible temperature indicators. These one-time use products undergo a phase change when they reach their rated temperature. Typically, this involves a sharply defined melting point that triggers an interaction between a chemical compound and a substrate to produce a permanent color change. CIs are primarily used for temperature monitoring and quality control. Supplied as an adhesive strip or label they denote whether temperature falls below or exceeds a rated threshold. Thermax® Irreversible temperature labels are available from 84 - 554⁰F. Designed to provide proof of attained temperature.