TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: The method further includes the steps of sensing a flow rate of gas that engages the catalyst and metal oxide layer over a fixed time period, calculating a cumulative value for the carbon monoxide adsorbed onto the metal oxide layer from the increase in temperature of the metal oxide layer due to the exothermic oxidation of the carbon monoxide, calculating a volume of gas by multiplying the flow rate by the fixed time period, and calculating a concentration of carbon monoxide in the gas as a function of the cumulative value and the volume. It also includes the steps of providing a reference cumulative value provided by a reference sensing element comprising the first catalyst dispersed over a layer of the metal oxide, heating the reference sensing element to the first temperature, recording any temperature increase of the reference sensing element above the first temperature, calculating a reference value from the temperature increase, and reducing the cumulative value for the carbon monoxide gas by the reference cumulative value. The reducing step is performed by differential amplification. The gas is filtered before it reaches the metal oxide layer. The catalyst is regenerated by heating the catalyst and metal oxide layer to at least 200 degrees C.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Catalyst: The catalyst is silver (Ag), gold (Au), ruthenium (Ru), rhodium (Rh), palladium (Pd), iridium (Ir), platinum (Pt), or their metallic alloys, preferably Pt and Ru. It can also be an RuPt alloy or RuIR alloy. The metal oxide layer is a refractory metal oxide, such as, alumina, silica, titania, or zirconia. The second metal oxide layer can be nickel oxide (NiO), zinc oxide (ZnO) and/or manganese dioxide (MnO2).    TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Components: The sensor further includes a heater. After the carbon monoxide has been adsorbed onto the metal oxide layer, the heater heats the sensing element to a first temperature. The heater is capable of heating the sensing element to a third temperature of at least 20 degrees C for regenerating the catalyst. The processing module determines accumulated carbon monoxide in accordance with the increase in temperature, and determines carbon monoxide concentration in accordance with the equation (I) as given in the image, where F is the flow rate signal and t is time.The sensor further includes a filter (20) is upstream of the sensing element, and a filter upstream of the flow rate sensor so that the flow rate sensor is between the filter and the sensing element. The metal oxide layer is a first metal oxide layer and the sensing element further comprises a second metal oxide layer disposed on top of the catalyst and the first metal oxide layer. A reference sensing element comprising the catalyst dispersed over a layer of the metal oxide is also included. The reference sensing element further includes a heater (16). The carbon monoxide sensor further includes a low temperature carbon monoxide oxidation catalyst dispersed on a substrate. The low temperature carbon monoxide oxidation catalyst and substrate are upstream of the reference sensing element. The reference sensing element is coupled to the processing module.