The structure of bacteriophage T7

The invention provides a method and apparatus for detecting impairment of the integrity of barriers used for the containment of fluid materials, particularly fluid materials at cryogenic temperatures, e.g., liquefied natural gas. The detection system employs electrical conductors which are in physical relationship to the barrier and undergo a change in current conducting function in the event of barrier failure. In the containment of fluid at low temperatures the detection system preferably comprises conductors which have temperature dependent resistances and are embedded within the thickness of the barrier. By distribution of conductors over different notional zones of the barrier area and provision of associated warning devices the location of leakage points within the barrier area can be automatically indicated.