GE - Rockford's Bleed Air Warning Systems perform the following functions:

• Monitor and detect overheat conditions in the pneumatic ducts
  When the monitored duct air temperature exceeds a predetermined temperature, the system controller lights a flight deck warning lamp to alert the crew.

• Monitor and detect leaks in the aircraft's pneumatic duct system.
  Detects leaks in aircraft's pneumatic duct system by sensing the temperature of the overheated air surrounding the leaking duct. Systems accurately determine the location of the overheat condition, annunciate overheat conditions to the aircraft's crew warning system, and stores the locating information for retrieval by the maintenance crew.