Abstract: A gas sensor includes a sensing element having an electrochemical cell and a reference gas channel in fluid communication with a reference electrode. A shield of the gas sensor is made of a metal material, the shield being hollow such that a chamber is located within the shield and such that the shield has an inner surface and an outer surface, the electrochemical cell being located outside of the chamber and the reference gas channel being in fluid communication with the chamber which provides fluid communication from the chamber to the reference electrode. The shield has a reference gas aperture extending through the metal material from the outer surface to the inner surface such that the reference gas aperture permits a reference gas to flow into the chamber while preventing liquid water from entering the chamber.