A system is provided for real-time, continuous, and accurate monitoring of the various states of the fermentation process in a closed fermentation vessel by monitoring the pressure created by the flow of carbon dioxide that is evolved as a consequence of the fermentation activity. The carbon dioxide transits through an orifice that has a flow area sufficient to maintain pressure in a range suitable for a pressure sensor with the electrical output thereof transmitted to an instrument that records and displays the pressure data to provide state information for use in algorithms to establish pre-alert warnings or alarms and provide correction control signals to ameliorate any anomalous condition detected.