The NOx formation during combustion in the diesel engine is predominantly NO and which is
converted to a minor extent to NO2 by oxidation either in the combustion space or in the exhaust gas
systems downstream (exhaust gas piping, exhaust gas turbo charger etc.). In general, exhaust gas leaving
the engine is 95% NO and approximately 5% NO2. To simulate the process of NO oxidation, to form
NO2 in the atmosphere, practically, all the legislation stipulate that in the calculation of NOx mass flow
emitted, the entire NOx must be taken as NO2. The N2O concentration in the exhaust gas of medium
speed diesel engines, burning heavy fuel is limited to a few ppm. Therefore, it can be neglected from the
viewpoint of environmental protection.