What are the environmental standards for automobiles?

[McArthur]

Automobile emission standards refer to regulations on the content of harmful gases such as CO (carbon monoxide), HC+NOx (hydrocarbons and nitrogen oxides), and PM (particulate matter, soot) emitted from vehicle exhaust. Automobile emissions refer to harmful gases discharged from exhaust. These gases are produced during the combustion process in the engine. The causes of these harmful gases vary: CO is an intermediate product of incomplete fuel oxidation and is produced when oxygen is insufficient. A rich air-fuel mixture or uneven mixture distribution can increase CO emissions. HC represents unburned fuel components, resulting from uneven mixture distribution or cold combustion chamber walls causing some fuel to be discharged without complete combustion. NOx is a substance produced during the combustion of fuel (gasoline). PM is also a substance generated when fuel burns under oxygen-deficient conditions, most notably in diesel engines. Since diesel engines use compression ignition, diesel fuel is more prone to cracking under high temperature and pressure, producing large amounts of visible soot.

[OThomas]

As someone who commutes by car every day, I've actually looked into the environmental standards. Basically, it's the threshold set by the government for vehicle exhaust emissions. The current mainstream China 6 standard is particularly strict, mainly controlling tailpipe pollutants like carbon monoxide, hydrocarbons, and nitrogen oxides. I remember all new cars must pass environmental certification before leaving the factory—those green labels from the DMV marked with China 5 or China 6 indicate the emission level. Older vehicles also get their exhaust tested during annual inspections; my neighbor's car recently failed and was required to undergo repairs due to excessive emissions. If you buy a new energy vehicle, there are basically no emission issues, but for traditional fuel vehicles, you'd better make sure it meets China 6 standards to be safe.

[Amara]

From an environmental perspective, automotive emission standards are essentially a lifeline. Having focused on environmental protection for many years, I know that a single conventional fuel-powered vehicle can pollute hundreds of cubic meters of air with its daily emissions. The limits set by China's National VI standards, such as particulate matter not exceeding 0.003 grams per kilometer, are all designed to protect urban air quality. Currently, 67 key cities nationwide have implemented the National VI-b standard, which is even stricter than European regulations. When people choose vehicles with higher environmental ratings during car replacements, they are contributing to haze reduction—especially during northern China's winter heating season, where removing one high-emission vehicle from the road can slightly decrease PM2.5 concentrations.

[BrodyLee]

With over a decade of experience in auto repair, I've found that environmental standards directly impact vehicle maintenance. The structure of the catalytic converter differs completely between China IV and China VI vehicles, with the new standards requiring the addition of a particulate filter to handle fine particles. Once, a customer complained about high fuel consumption in their new car—it turned out to be the particulate filter burning extra fuel during regeneration. The most common causes of emission test failures are faulty oxygen sensors or clogged fuel injectors, with trouble code P0420 indicating low catalytic converter efficiency. Nowadays, repair shops must upgrade their diagnostic equipment to match newer models, as the old method of visually inspecting exhaust is completely ineffective.

[AlexaRose]

The matter of automotive emission standards has evolved over more than two decades since the implementation of China I in 2001, progressing to the current China VI. From what I've gathered in policy documents, the differences between China VIa and China VIb mainly lie in the transition period and implementation timelines. For instance, China VIb mandates that non-methane hydrocarbon emissions must not exceed 0.035 grams per kilometer. In reality, implementation timelines vary across regions—the Pearl River Delta adopted the new standard two years ahead of the national schedule. Rumor has it that the draft for China VII standards proposes real-time emission monitoring, which is likely to make fuel-powered vehicles increasingly difficult to sell. This also explains why new energy vehicles are developing so rapidly these days.