Tamper evident system

摘要

A tamper evident system for indicating when a closed enclosure (24) has been opened comprises a window (21) and a sensor (22) colour sensitive to presence of a gas. The sensor (22) is located in the enclosure (24) so as to be visible through the window (21). Any compositional change of gas in the enclosure (24) is signalled by a change of colour of the sensor (22).