This standard specifies requirements and provides guidance for the selection@ design specification@ mechanical description@ operation@ maintenance@ and test procedures for post-combustion NOx control equipment and related mechanical systems and components used for fired equipment in petrochemical and general refinery service. This document covers the following methods of post-combustion NOx reduction for both new and retrofit applications: ?? Selective Non-catalytic Reduction (SNCR)@ and ?? Selective Catalytic Reduction (SCR). This standard is primarily intended for direct application to fired process heaters@ reformers@ and industrial and power boilers used in petrochemical and general refinery services. The same fundamental NOx control technologies and systems may also be applied to Fluid Catalytic Cracking Units (FCCUs)@ incinerators@ gas turbine exhaust@ and other exhaust gas process systems; however@ SCRs may require additional considerations beyond the scope of this standard to address unique aspects@ such as high particulate content and corrosive chemicals@ in the flue gas stream. This document does not cover: ?? reduced NOx formation through combustion controls and design techniques such as low-NOx burners@ flue gas recirculation (FGR)@ and staged combustion; or ?? non-selective catalytic reduction (NSCR) for the control of NOx and other pollutant emissions. For further guidance on post-combustion NOx control process selection and the application of SNCR and SCR systems@ refer to Annex A. For further guidance on the process description of SNCR and SCR technologies and systems@ refer to Annex B and Annex C@ respectively. For further guidance on reactant storage@ distribution@ control@ and injection systems@ and general design considerations@ including purchaser decisions for SNCR and SCR systems@ refer to Annex D and Annex E@ respectively.