Abstract: An inflammable gas detector for detecting an inflammable gas wherein the inflammable gas detector is of the platinum-alloy wire type which forms part of a resistance bridge network to operate in a condition for maximum sensitivity by preadjusting the voltage at the terminals of the inflammable gas detector in accordance with the desired type of gas to be detected, then utilizing the signals supplied by the detector in the resistance bridge network to bring the cathode of a diode to the threshold limit value and at the same time to render two further diodes conductive to activate a signal or control relay or both.