An electrochemical sensor system for monitoring emissions includes locating first and second electrodes in a position to sense the emissions. At least one of the first and second electrodes is made of a dense electrode material. An ion-conductor material that acts as an electrolyte is operatively connected to the first and second electrodes. The first electrode is excited at a frequency f.sub.1, A response is received from the first electrode at frequency f.sub.1. A second signal is received base on the emissions and a response is produced indicating the emissions.
STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT
 The United States Government has rights in this invention pursuant to Contract No. DE-AC52-07NA27344 between the United States Department of Energy and Lawrence Livermore National Security, LLC for the operation of Lawrence Livermore National Laboratory.