Avery Dennison says its TT (Time-Temperature) Sensor active labels for time-temperature indication ensure temperature integrity throughout the cold chain. The labels include an indicator and activator label. Time-temperature monitoring does not begin until the activator label is applied to the indicator label, which is then immediately affixed to the package. No refrigeration of the labels prior to application is required. Once activated, the label will change color from yellow to pink at a pre-determined rate based on temperature exposure. Because it is not enzyme-based, the label delivers temperature-abuse indication even when exposed to excessive heat.