Patent ID: 8024958

Claim:
A gas sensor comprising: a planar substrate; a heater carried by the substrate; a temperature sensor that detects a temperature of the substrate proximate the heater; a catalyst carried by the substrate, the catalyst exhibiting a predetermined first area; and a gas impermeable layer formed adjacent to the catalyst, the layer defines a predetermined gas inflow region on the catalyst with the inflow region having a second area a predetermined amount less than the first area, wherein the whole of the catalyst is encapsulated by the substrate and gas impermeable layer, wherein an outside surface except for the gas inflow port is completely covered and in continuous direct contact with at least one of the substrate and gas impermeable layer, wherein the layer overlays the catalyst and defines one of, an annular gas inflow region, a gas inflow region formed as an area on an edge of an elongated catalyst, or a gas inflow region formed as an area on a selected surface of the catalyst, and wherein at least a portion of the inflow region is covered by a selected protective layer.