a conveyor assembly 18 that detects bags that leak . the assembly 18 includes a first conveyor 24 that operates in unison with a second conveyor 29 . the conveyors 24 and 29 confine the bags in chambers , with the bags being engaged by pressure assemblies 50 so that the bags that leak are reduced in volume . the bags are engaged at a downstream position and at an upstream position by detection devices 44 that provide a signal indicative of the volume of each bag . these signals are compared to thereby identify bags that leak .