What does IV represent in terms of national emission standards?

[MorganMarie]

IV refers to China 4. Below is an introduction to the China 4 standard: 1. The China Phase IV Motor Vehicle Pollutant Emission Standard, abbreviated as the "China 4 Emission Standard" or "China IV Standard," is slightly more lenient in emission limits for in-use vehicles compared to new vehicles under the China 4 standard. However, it is 34% stricter than the China 3 standard limits. In Beijing, China 4 vehicles initially undergo inspections every two years, and some China 4 vehicles are gradually starting to require annual inspections. During these inspections, vehicle emissions must meet the announced standard limits; otherwise, maintenance and repairs are necessary to pass the inspection. 2. The China 4 emission standard was implemented in 2011 and remained in effect until the introduction of the China 5 standard in 2018. The China 4 standard requires that the emissions of various pollutants be approximately 50% lower than those under the China 3 standard.