Apparatus and methods for measuring NOx concentrations are disclosed. One method includes the steps of providing a gas stream having a NO concentration and a NO2 concentration, wherein a sum of the NO concentration and the NO2 concentration is a total NOx concentration; contacting the gas stream with...http://www.google.com/patents/US7820028?utm_source=gb-gplus-sharePatent US7820028 - Oxides of nitrogen gas sensors and methods
