What do China III and China IV mean for vehicles?

[AlexandraRose]

China III and China IV refer to the emission standards for vehicle exhaust. The China IV emission standard is stricter than China III. The National Third Stage Motor Vehicle Pollutant Emission Standard, abbreviated as China III, is equivalent to the Euro 1 emission standard, meaning the pollutant content in the exhaust is similar to Euro 1. The difference is that new vehicles must be equipped with an OBD (On-Board Diagnostics) system. The OBD system features an increased number of detection points and monitoring systems, with oxygen sensors installed at both the inlet and outlet of the three-way catalytic converter to ensure compliance by real-time monitoring of vehicle emissions. The National Fourth Stage Motor Vehicle Pollutant Emission Standard, abbreviated as China IV, targets major vehicle pollutants such as hydrocarbons, nitrogen oxides, carbon monoxide, and particulate matter. The China IV standard controls and reduces vehicle emissions below specified limits through technologies like the active layer of the catalytic converter, secondary air injection, and exhaust gas recirculation systems with cooling devices.