Some embodiments for a fault detection apparatus may include one or more monitors to detect at least three operating states of a sensor, such as pass, fail, and inoperative so as to enable a manufacturing facility to differentiate between situations in which a container does not have the appropriate machine-readable label and situations wherein the sensor is actually inoperative. The fail state may be indicative of an object on a conveyor system not matching a predetermined description, identity or characteristic. The pass state may be indicative of an object on a conveyor system matching the predetermined description, identity or characteristic. The inoperative state may be indicative of a sensor output associated with a malfunction in the sensor itself. The fault detection apparatus may also include a fail-to-safe controller configured to detect these operating states.