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Emission Standards: A Global Perspective

  • Lexicon
  • 4 min read
Emission Standards EU US

What are the Emission Standards?

Emission standards, known as “Tier” or “Stage” depending on the region, play a crucial role in regulating exhaust emissions from various vehicles, including agricultural and heavy-duty machinery. These standards are enforced in both the European Union and North America, with vehicles failing to meet these regulations prohibited from operating within these territories.

The implementation of emission standards is vital for environmental protection and sustainability, reflecting a commitment to reducing pollution and mitigating climate change.

Tier 1, Tier 2, Tier 3, Tier 4 emission standards


What are the Emission Standards in European Union? (EURO5/EURO6)

In the European Union, transportation accounts for a significant portion of gas emissions, making it imperative to regulate vehicle emissions effectively. The EU has established emission standards based on the grams of CO2 emitted per kilometre travelled. Initially set at 130 grams per kilometer from 2012 to 2015, the limit was subsequently tightened to 95 grams per kilometre after 2021, demonstrating a commitment to reducing environmental impact.

The EU has introduced several emission standards, including Euro 4, Euro 5, and Euro 6, aimed at controlling pollutants emitted by vehicles. Euro 4 came into effect in 2008, followed by Euro 5 in 2010, and Euro 6 in 2014. These standards represent significant milestones in combating climate change and promoting sustainable transportation practices, emphasizing the need for cleaner and more efficient vehicles.

Euro 4 set the stage for stricter emission control, introducing limits on particulate matter (PM) and nitrogen oxide (NOx) emissions. Euro 5 further tightened these limits, incorporating more stringent requirements for diesel particulate filters (DPF) and selective catalytic reduction (SCR) systems to reduce NOx emissions. Euro 6, the latest standard, introduced even lower emission limits, including tighter restrictions on NOx emissions and additional requirements for on-board diagnostics (OBD) to monitor vehicle emissions in real-time.

Vehicle Emission History and Future


What are the Emission Standards in North America? (Tier/Stage)

In North America, the implementation of emission standards began with Tier 1, targeting engines with more than 37 kW of power between 1996 and 2000. Subsequent regulations introduced Tier 2 and Tier 3 standards for engines with varying power outputs. Notably, Tier 4 standards, introduced between 2008 and 2015, aimed to reduce emissions by 90% and mandated the use of urea-based solutions and diesel particulate filters to achieve this goal.

Tier 4 marked a significant milestone in emission control technology, requiring the adoption of advanced exhaust after-treatment systems such as selective catalytic reduction (SCR) and diesel oxidation catalysts (DOC) to meet stringent emission limits. SCR systems utilize a urea-based solution, known as diesel exhaust fluid (DEF), to chemically convert harmful nitrogen oxides (NOx) into nitrogen and water vapour, thereby reducing NOx emissions by up to 90%.

Looking ahead, the development of Tier 5 emission standards is underway, with anticipated implementation between 2028 and 2030. The focus of Tier 5 is to further reduce particulate matter (PM) and nitrogen oxide (NOx) emissions by up to 90%, building on the progress made with previous tiers. Proposals include the utilization of low load certification test cycles to evaluate emissions accurately.



Emission standards play a critical role in regulating vehicle emissions globally, with both the EU and North America implementing regulations to reduce pollution and protect the environment. By adhering to these standards and embracing cleaner technologies, the automotive industry can contribute to a more sustainable future for generations to come. From Euro standards in Europe to Tier standards in North America, the commitment to cleaner air and reduced emissions remains paramount in shaping the future of transportation.