A system and method for monitoring the concentration of a gas in an enclosed space into which the gas is being injected by a gas injection system. The system includes means for carrying out the method that includes measuring a parameter indicative of gas concentration using a gas sensor, comparing the parameter with a predetermined limit value of the parameter using a microprocessor, and if the parameter is greater than the predetermined limit value then activating a shut-off of the gas injection system. Furthermore, continuously monitoring at least one of a hardware element, a software function and a control signal used to carry out the method to identify faults in at least one of the hardware element, the software function and the control signal and if a fault is detected activating the shut-off of the gas injection system.
