A system for providing inert gas to a protected space, comprising: a protected space comprising a fuel tank ullage space, a cargo hold, or an equipment bay; an electrochemical cell comprising a cathode and an anode separated by a separator comprising a proton transfer medium; a power source arranged to provide a voltage differential between the anode and the cathode; a cathode fluid flow path in operative fluid communication with the cathode between a cathode fluid flow path inlet and a cathode fluid flow path outlet; an anode fluid flow path in operative fluid communication with the anode, between an anode fluid flow path inlet and an anode fluid flow path outlet; a cathode supply fluid flow path between an air source and the cathode fluid flow path inlet, and an inert gas flow path in operative fluid communication with the cathode fluid flow path outlet and the protected space; an anode supply fluid flow path between a process water source and the anode fluid flow path inlet; a process water fluid flow path in operative fluid communication with the anode fluid flow path inlet and the anode fluid flow path outlet; a baffle disposed on the process water fluid flow path: a gas outlet from the process water fluid flow path in operative fluid communication with the baffle; a sensor configured to directly or indirectly measure dissolved oxygen content of process water received by the baffle; and a controller configured to provide a target response of the sensor through control of a flow rate of process water or a temperature of process water, or both a flow rate and a temperature of process water. a protected space comprising a fuel tank ullage space, a cargo hold, or an equipment bay; an electrochemical cell comprising a cathode and an anode separated by a separator comprising a proton transfer medium; a power source arranged to provide a voltage differential between the anode and the cathode; a cathode fluid flow path in operative fluid communication with the cathode between a cathode fluid flow path inlet and a cathode fluid flow path outlet; an anode fluid flow path in operative fluid communication with the anode, between an anode fluid flow path inlet and an anode fluid flow path outlet; a cathode supply fluid flow path between an air source and the cathode fluid flow path inlet, and an inert gas flow path in operative fluid communication with the cathode fluid flow path outlet and the protected space; an anode supply fluid flow path between a process water source and the anode fluid flow path inlet; a process water fluid flow path in operative fluid communication with the anode fluid flow path inlet and the anode fluid flow path outlet; a baffle disposed on the process water fluid flow path: a gas outlet from the process water fluid flow path in operative fluid communication with the baffle; a sensor configured to directly or indirectly measure dissolved oxygen content of process water received by the baffle; and a controller configured to provide a target response of the sensor through control of a flow rate of process water or a temperature of process water, or both a flow rate and a temperature of process water. a gas outlet from the process water fluid flow path in operative fluid communication with the baffle; a sensor configured to directly or indirectly measure dissolved oxygen content of process water received by the baffle; and a controller configured to provide a target response of the sensor through control of a flow rate of process water or a temperature of process water, or both a flow rate and a temperature of process water.