This SAE Recommended Practice applies to nomenclature of emissions and emissions reduction apparatus as applied to various engines and vehicles. Modifying adjectives are omitted in some cases for the sake of simplicity. However, it is considered good practice to use such adjectives when they add to clarity and understanding.

Purpose—This document was prepared to standardize terminology and nomenclature in order to facilitate clearer understanding for engineering discussions, comparisons, and the preparation of technical papers.