Abstract: An electrochemical sensor for detecting gas includes stacked reference, counter and sensing electrodes within a body and having a quantity of a liquid electrolyte in an electrolyte chamber therein. A support is provided for holding the electrodes and mats in contact with each other and at an inner end of a cavity within the sensor. A gas passage, such as a diffusion limiter, is provided through the sensor body and permits gas to reach the sensing electrode. The reference electrode is formed in a wraparound structure, with the reference electrode provided with a plurality of integral extensions which extend around the support and the counter electrode and into contact with the liquid electrolyte, thereby providing a large reference electrode fitted into a small body.