Abstract: Apparatus for seal-testing packages to enable only sealed packages to be processed. The apparatus includes one or more carrier devices for receiving packages at a receiving station and carrying them to a delivery station. Each carrier device receives a package between a pair of opposed pressure members, means being included to close the pressure members and hence compress the package during passage from the receiving station. A detector produces an output signal in the event that the pressure members have been closed by more than a predetermined amount when the carrier device reaches the delivery station.