A smoke detection sensor ion chamber has a leakage current that is dependent upon the permittivity of the ionized gas (air) in the chamber. Smoke from typical fires is mainly composed of unbumed carbon that has diffused in the surrounding air and rises with the heat of the fire. The permittivity of the carbon particles is about 10 to 15 times the permittivity of clean air. The addition of the carbon particles into the air in the ion chamber changes the permittivity thereof that is large enough to detect by measuring a change in the leakage current of the ion chamber.