China VI Emission Standards

China VI Emission Standards, formally known as the "Limits and measurement methods for emissions from light-duty vehicles (CHINA 6)" (GB 18352.6—2016) and "Limits and measurement methods for emissions from heavy-duty diesel vehicles (CHINA 6)" (GB 17691—2018), represent the most stringent automotive exhaust emission regulations currently enforced in China. Gazetted in 2016, the China VI standards were rolled out in two phases: China 6a took effect nationwide for light-duty vehicles on 1 July 2020, followed by the comprehensive rollout of China 6b on 1 July 2023. With threshold limits on par with the highest international benchmarks, it is widely recognised as one of the toughest vehicle emission frameworks in the world.

Substantial Tightening of Major Pollutant Limits

Compared to the preceding China V standards, China VI drastically lowers the permissible limits across major exhaust pollutants. Taking light-duty petrol vehicles as an example:

• Carbon Monoxide (CO): The China 6a limit is set at 0.70 g/km and China 6b at 0.50 g/km, representing a 30% and 50% reduction respectively compared to China V (1.00 g/km).

• Nitrogen Oxides (NOx): The China 6b limit is capped at 0.035 g/km, down 42% from the 0.060 g/km threshold under China V.

• Total Hydrocarbons (THC): China 6b enforces a ceiling of 0.10 g/km, slashed by 50% compared to China V's 0.20 g/km.

• Particulate Matter (PM): China VI establishes a dedicated PM limit (0.0045 g/km) for petrol vehicles for the first time, addressing an area unregulated under the China V era.

• Particle Number (PN): A new regulatory limit governing particle numbers for petrol vehicles (6.0×10¹¹ particles/km) was introduced under China VI, closing a previous technical loophole in China V.

Introduction of Real Driving Emissions (RDE) Testing

The China VI standard officially incorporates Real Driving Emissions (RDE) testing into mandatory homologation requirements for the first time. RDE testing utilises Portable Emission Measurement Systems (PEMS) to record tailpipe emissions under actual on-road driving conditions rather than solely relying on laboratory chassis dynamometers, spanning urban, suburban, and highway driving profiles.

The introduction of RDE testing means that a vehicle will fail compliance if its on-road emissions breach regulatory caps, even if it passes laboratory assessments. This effectively bridges the gap between lab test cycles and real-world driving conditions, ensuring emissions control systems remain effective across all driving scenarios.

Stricter Controls on Evaporative and Refuelling Emissions

China VI significantly tightens evaporative emission requirements, mandating sealed housing evaporative determination tests in laboratories to simulate fuel vapour leaks during both parking and driving cycles. For petrol models, Onboard Refuelling Vapour Recovery (ORVR) has been introduced, requiring fuel vapours during refuelling to be channelled directly into the onboard carbon canister rather than vented into the atmosphere, further cutting volatile organic compound (VOC) emissions.

Powertrain Upgrades and Industry Impact

To comply with China VI mandates, carmakers have undertaken extensive hardware and software overhauls. Petrol vehicles are now universally equipped with combined Three-Way Catalytic Converters (TWC) and Gasoline Particulate Filters (GPF), alongside higher-precision direct fuel injection and closed-loop management systems on performance variants. Diesel vehicles require a far more complex exhaust aftertreatment suite, integrating Diesel Oxidation Catalysts (DOC), Diesel Particulate Filters (DPF), Selective Catalytic Reduction (SCR), and Ammonia Slip Catalysts (ASC), supported by standard AdBlue (aqueous urea solution) injection to neutralise NOx emissions.

The implementation of China VI has noticeably driven up per-vehicle production costs and accelerated the phase-out of technologically obsolete powertrains. Amid the rapid market penetration of new energy vehicles (NEVs), China VI standards, alongside the overarching electrification push, have accelerated decarbonisation across the automotive sector, steering internal combustion engines toward hybridisation and alternative fuel developments.

In-Service Conformity and Compliance Monitoring

China VI also significantly steps up surveillance on vehicles already on the road. Environmental authorities monitor and audit real-world fleet emissions through remote sensing systems, roadside spot-checks, and periodic vehicle inspections. Vehicles found exceeding emission thresholds face mandatory rectification orders within a set timeframe alongside regional driving restrictions, ensuring exhaust aftertreatment hardware remains fully operational throughout the vehicle's entire operational lifecycle.