Indicator devices, primarily labels, reveal the passage of time, temperature excursions beyond acceptable limits, or both. Many of these devices have been designed for the food industry but have potential applications in the pharmaceutical supply chain.One temperature indicator designed to protect red blood cells is attached to the blood bag with a handheld activator. After preconditioning, activation, and application, phase-change material in the label irreversibly turns from white to red if the temperature of the contents exceeds a preset threshold ("Check-Spot" label with "Spot-Gun" handheld activator, Harald H. Temmel KEG, Gleisdorf, Austria).
Some labels monitor time rather than temperature. One technology that can be supplied as an external label or integrated into the packaging is particularly useful for products such as eyedrops, which must be used within a specific time frame. When activated, an edible oil travels across the label at a consistent rate and provides a visible indicator of how long the product has been open or in use ("Timestrip" label, Timestrip plc).
Another time-tracking option is a small, battery-equipped digital counter with a magnetic or suction-cup backing for easy mounting ("Days Ago" digital day counter, double u products, Inc., Cupertino, CA).
An indicator that registers both time and temperature consists of a clear pressure-sensitive label with a coating of food-grade microorganisms that simulate the degradation of the product. When the label is activated and applied over the barcode of the product, it slowly changes color as time passes or temperatures exceed its threshold. When the label becomes so opaque that the barcode is unreadable, the product is no longer safe to use ("Traceo" label, Cryolog, Gentilly, France).
For storage facilities, monitoring systems can provide alerts if temperatures warm or chill too much or the power fails. Light-emitting diodes on a sealed, weatherproof, lockable enclosure display alarm and status conditions for at-a-glance monitoring. Capable of measuring temperatures as low as –85 °C, the monitoring system automatically calls as many as eight numbers when a problem occurs. The unit also can trip an on-premises warning device ("Sensaphone 1400" and "Sensaphone 1800," Sensaphone, Inc., Aston, PA).
Data loggers and RFID
For cold-chain applications, data loggers help ensure products remain within storage parameters during shipment by providing a record of the conditions experienced. Some of today's units are low-cost enough to be used for a single trip and often incorporate radio-frequency identification (RFID) technology to automate data transmission.