Patent ID: 8323574

Claim:
An apparatus for reducing a nitrogen oxide gas emitted by a emissions source, comprising (a) an emissions source, (b) an exhaust conduit for transporting the nitrogen oxide gas downstream from the emissions source, (c) an injector for injecting a reducing agent into the conduit, and (d) one or more gas analyzers located in the conduit upstream from the injector, wherein a gas analyzer comprises an array of chemo/electro-active materials selected as a member from the group of five arrays of chemo/electro-active material consisting of: (i) an array comprising SnO x , Nb a Ti b O x , and Ni a Zn b O x ; (ii) an array comprising ZnO x , Ti a Zn b O x , and Ta a Ti b O x ; (iii) an array comprising Sb a Sn b O x , Ta a Ti b O x , and Ti a Zn b O x ; (iv) an array comprising SnO x , Ta a Ti b O x , and Ti a Zn b O x ; and (v) an array comprising Ni a Zn b O x , SnO x , and Ta a Ti b O x ; wherein a, b and c are each independently about 0.0005 to about 1; and wherein x is a number sufficient so that the oxygen present balances the charges of the other elements in the chemo/electro-active material.