The ampoule fractures when exposed to specific temperatures irreversibly staining the paper behind to indicate the product has been exposed to unacceptable temperatures. When placed directly on secondary shipper boxes of temperature sensitive products during shipment and storage, the 3M Freeze Watch Indicator provides a reliable measure of temperature exposure. Pressure sensitive adhesive sticks to almost all clean, dry surfaces for a strong bond that securely holds the indicator in place throughout the shipping process. These indicators are ideal for monitoring products that are susceptible to damage when exposed to freezing temperatures during shipment and storage.When all packaging requirements have been followed and precautions observed, 3M Freeze Watch Indicators add a critical layer of content security by providing a noticeable indication that the package and contents were exposed to freezing temperatures.