Chemiluminescence is the word given to describe a chemical reaction which produces light.  In this instance it is the reaction between nitric oxide, NO and ozone.  Each reaction produces a photon of light, therefore from the amount of light produced it is possible to deduce the number of molecules of NO in the reaction chamber, and hence the concentration.

This method is specific to NO and so has no cross sensitivity to other gases that might be present in your sample.  CO and H2O can act to absorb the light, a quenching effect, and so a reaction chamber under vacuum can be utilised to reduce this effect where accurate readings are required.

Signal manufacture a range of analysers for NOx using chemiluminescence, heated, vaccum and ambient according to performance requirement and budget constraints.

4000VM Heated Vacuum NO/NO2/NOx Analyser

4000VMA Heated NO/NO2/NOx Analyser