Chemiluminescent analyzers for gaseous analysis represent a significant advance over manual or automated wet chemical analytical techniques because no aqueous reagents are required, the instrumental determination of the species of interest is available in real time (∼ 1–5 seconds response time), and the instrumental techniques show few interferences. Additional advantages are linearity, sensitivity and ease of use over a wide dynamic measurement range. Gas phase chemiluminescence is defined as the production of visible or infrared radiation by the reaction of two gaseous species to form an excited species product that decays to its ground state by the photoemissive act. Other possibilities exist for the decay of the excited species; instrumental design attempts to minimize deactivation by non-photoemissive events such as collision with a chamber wall or third body gaseous species.