A leak detection apparatus for aircraft bleed air systems includes a supporting spacer positioned within the shroud and supported upon the bleed air duct of the aircraft. A sleeve supported on the exterior of the shroud further supports a plenum having generally cylindrical sensor tubes through which sensor wire sets pass. A director positioned within the shroud above the bleed air duct is coupled to a generally cylindrical accumulator which in turn is in communication with the plenum. Appropriate apertures are provided to vent and direct bleed air from the shroud interior to the sensor wire sets and thereafter vent outwardly into cooler ambient air. The sensor wire sets respond to the temperature of the bleed air leakage to trigger alarm apparatus.