A gas sensor is disclosed comprising an oxygen pump cell having at least one exterior pump electrode (40, 42) and at least one interior pump electrode (44, 46) disposed on opposite sides of a first solid electrolyte layer (30). An emf cell having a first and second emf electrodes (50, 52) and first and second reference gas electrodes (54, 56) are disposed on opposite sides of a second solid electrolyte layer (32). At least one insulating layer (22) is in contact with the first and second emf electrodes (50, 52). At least one via hole (60, 62) is disposed through the first solid electrolyte layer (30). At least one air channel (80, 82) is disposed through at least one insulating layer (22). An air vent (84) is disposed in at least one insulating layer (24) in contact with the first and second reference gas electrodes (54, 56). A heater (934) is disposed in thermal communication with the sensor. And at least five electrical leads are in electrical communication with said sensor. A method of using a gas sensor is also disclosed.