This unit was designed to control and prevent hazards associated with the presence of toxic atmosphere in all applications where forced ventilation or devices not at ambient temperature, such as ovens, cold-rooms and combustion chambers, make it impossible to use traditional systems. The unit is often used to monitor industrial processes and protect many work environments where there is a risk of toxicity. The sensor comprises an electrochemical cell with replaceable cartridge and is housed in an ATEX CESI Exd IIC T6 certified sintered explosion-proof filter. The unit has an automatic washing system, an input for enabling or disabling analysis, and a flow control switch with alarm. The pre-alarm relay and then the alarm relay are triggered when flammable gases are detected. There is also a 4-20 mA output for connecting the unit to external gas plants.