Patent ID: 7678253

Claim:
An electrochemical sensor for the detection of atmospheric gases or vapors, said sensor comprising an insulating substrate upon which are at least two electrodes, said electrodes closely space but not in contact with each other and the at least two electrodes are in contact with an electrolyte, containing a fluid medium that allows the movement of electrically charged ions, an external circuit that applies an electrical potential between at least two of the electrodes, a first electrode that is held at an electrical potential that is positive with respect to a second electrode, and the first electrode and at least part of the medium is exposed to the ambient air such that any target gases present in the air can reach and contact the first electrode and electrolyte, the first electrode being comprised of a metal that at least a component of which can be oxidized in the presence of a target gas so as to produce ions in the medium that are mobile and furthermore, the composition of said ions and the electrical potential are chosen such that said ions will be reduced at the second electrode so as to produce a metallic deposit in electrical contact with the second electrode; said sensor when in use is in contact with an external electrical circuit that maintain the potential between the first and second electrodes and monitors the resistance of the electrical pathway between the first and second electrodes such that the said circuit will provide an indication of the resistance of the path between the first and second electrodes and will provide an indication to the user if the resistance falls below a predetermined threshold.