(EP771418-A1)      A device for measuring the amt. of a reactive component in a single or mixed gas (in which at least one gas reacts with the reactive component) comprises: a reaction chamber (2); contg. means (4) for supporting a removable catalyst (8); and an adjacent heat sensor (6). The sensor (6) measures the heat released or absorbed by any catalysed reaction and generates a representative electrical signal. The catalyst (8) may be positioned at two different locations along with separate adjacent heat sensors (6). If so, the support (4) limits the gas exchange rate between the catalyst (8) and the test gas at one of the locations, to 0.1-5.0% of the exchange rate at the other location.    USE -   For detecting potentially explosive gas mixtures at low pressures.    ADVANTAGE -   Can detect small amounts of methane in air, or oxygen in hydrogen, deuterium or tritium gas having a pressure of less than 10 mbar.    (JP10503013-W)      A device for measuring the amt. of a reactive component in a single or mixed gas (in which at least one gas reacts with the reactive component) comprises: a reaction chamber (2); contg. means (4) for supporting a removable catalyst (8); and an adjacent heat sensor (6). The sensor (6) measures the heat released or absorbed by any catalysed reaction and generates a representative electrical signal. The catalyst (8) may be positioned at two different locations along with separate adjacent heat sensors (6). If so, the support (4) limits the gas exchange rate between the catalyst (8) and the test gas at one of the locations, to 0.1-5.0% of the exchange rate at the other location.    USE -   For detecting potentially explosive gas mixtures at low pressures.    ADVANTAGE -   Can detect small amounts of methane in air, or oxygen in hydrogen, deuterium or tritium gas having a pressure of less than 10 mbar.    (EP771418-B1)      A device for measuring the amt. of a reactive component in a single or mixed gas (in which at least one gas reacts with the reactive component) comprises: a reaction chamber (2); contg. means (4) for supporting a removable catalyst (8); and an adjacent heat sensor (6). The sensor (6) measures the heat released or absorbed by any catalysed reaction and generates a representative electrical signal. The catalyst (8) may be positioned at two different locations along with separate adjacent heat sensors (6). If so, the support (4) limits the gas exchange rate between the catalyst (8) and the test gas at one of the locations, to 0.1-5.0% of the exchange rate at the other location.    USE -   For detecting potentially explosive gas mixtures at low pressures.    ADVANTAGE -   Can detect small amounts of methane in air, or oxygen in hydrogen, deuterium or tritium gas having a pressure of less than 10 mbar.