A corrugator includes a separation sensor for sensing separation of a corrugated medium and liner of a corrugated paperboard. Sensing the separation, also known as blowout or fluff out, allows the corrugator to be controlled to prevent problems which arise when corrugated paperboard having such a separation continues downstream along the corrugator. Typically, the corrugator is operated to cease downstream movement of the paperboard while a faulty segment which includes the separation is removed and the problem causing the separation is fixed, thereby providing for subsequent production of corrugated paperboard which is properly glued.