What does National IV refer to?

[JamesonMarie]

National IV refers to China 4. Below is the relevant introduction to the China 4 standard: 1. The National Fourth Stage Motor Vehicle Pollutant Emission Standard, abbreviated as the "China 4 Emission Standard" or "National IV Standard," has relatively looser emission limits for in-use vehicles compared to new vehicles under the China 4 standard. However, it is still 34% stricter than the limits of the China 3 standard. In Beijing, National IV vehicles are initially inspected every two years, and some National IV vehicles are gradually starting to undergo annual inspections. During these inspections, the vehicle's emissions must meet the published standard limits; otherwise, maintenance is required, and the vehicle must pass the inspection to be cleared. 2. The China 4 emission standard was implemented starting in 2011 and remained in effect until 2018 when the China 5 standard was introduced. The China 4 standard requires that the emission levels of various pollutants be approximately 50% lower than those of the China 3 standard.