Abstract: A Solid State Electrolytic Cell Gas Sensor is presented which is capable of measuring various toxic or combustible gases in low concentrations (0-5 PPM) up to and including high concentrations such as 0-20 percent by volume. The sensor exhibits excellent specificity to the gas designated to be detected. The sensor causes the dissociation of the gases into charged species such as ions and complex ions and does not operate by changing its electro-conductivity in response to the adsorption of the gas. The sensor has an electrical signal which is a function of the type and concentration of gas and which is also a function of the collection of ions by transport process. The solid state material from which the sensor is fabricated is produced by the method of addition of one or more metal oxides to a non-metal oxide with a general formula of MxOy - NpOq. M can be a metal from the transition elements and N can be a non-metal of group III and IV from the periodic table.