COD is a term used to measure the quality of water. It is a measure of water pollution on resulting from organic matier. This Parameter is defined as the amount of oxygen (in milligrams per liter of sample) required, for the Oxidtion of all organic matier contained in a water sample. Cod limits are set by competent authorities for various effluents permissible for accepting them in Effluent Treatment Plant or for releasing them to the environment. Among the various methods and instruments available, a non-dispersive absorption based instrument has been found to been found to be the best for this. The V-Tech COD Analyzer is based on the above principle.