According to IMO regulations, a Technical File shall be made for each engine. This Technical File contains information about the components affecting NOx emissions, and each critical component is marked with a special IMO number. Such critical components are the injection nozzle, injection pump, camshaft, cylinder head, piston, connecting rod, charge air cooler and turbocharger. The allowable setting values and parameters for running the engine are also specified in the Technical File.
The marked components can later, onboard the ship, be easily identified by the class surveyor and thus an International Air Pollution Prevention (IAPP) certificate can be issued.