What are the letter designations for China's emission standards?
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Ⅰ China I emission standard, Ⅱ China II emission standard, III China III emission standard, Ⅳ China IV emission standard, V China V emission standard, Ⅵ China VI emission standard. Below is a detailed introduction to national emission standards: 1. Vehicle emissions: Vehicle emissions refer to harmful gases discharged from exhaust, including CO (carbon monoxide), HC, NOx (hydrocarbons and nitrogen oxides), PM (particulate matter, soot), etc. These are all harmful gases produced during engine combustion. The causes of these harmful gases vary: CO is an intermediate product of incomplete fuel oxidation, occurring when oxygen is insufficient; rich fuel mixture and uneven mixture distribution increase CO emissions. HC represents unburned fuel components, caused by uneven mixture distribution or combustion chamber wall cooling leading to incomplete combustion. NOx is produced during gasoline combustion. PM is generated during fuel combustion under oxygen-deficient conditions, most notably in diesel engines due to their compression ignition method where diesel fuel cracks under high temperature and pressure, producing visible soot particles. 2. National standards: Mandatory national standards shall be established for technical requirements that protect human health, life and property safety, national security, ecological environment safety, and meet basic socioeconomic management needs.