An overview of heavy duty diesel emissions standards

Nathan Business Development Manager Quebec Posted  

Over the last 15 years, diesel technology has changed at an incredible rate, driven by ever tightening regulations on tailpipe emissions. We have found that many teachers, technicians and students have difficulties navigating the labyrinth of standards.

We put together this document to help give an overview and clarify diesel emissions standards.

I was unable to upload the PDF, so here is a link to the document.

I hope you find this helpful, 

Nathan …

Below is a copy and pasted incomplete excerpt of the document: 

Diesel emissions standards in North America and worldwide are difficult to understand for technicians, students and teachers alike. At ConsuLab, we continue to develop our expertise in teaching diesel emissions. Our OEM relationships with Caterpillar, Cummins and John Deere, keep us at the leading edge of aftertreatment systems and emissions control technologies Schools are challenged to refresh their engine fleet and faced with difficult purchasing choices choosing between technology of emission standards that best fit their program.

To help clarify these choices we wish to share our expertise and demystify some of the nomenclature and standards without going into minutiae.


EPA - Environmental Protection Agency sets standards for all vehicle emissions in the United States. When discussing an EPA standard, we use a reference year in a format of EPA following the reference year (example: EPA2007). This standard is used discussing on-highway class 8 trucks with diesel engines in Canada and the United States. This standard measures engine exhaust emissions at the tailpipe.

Tier level – while still governed by the EPA, we refer to a Tier standard (example: Tier 3). The Tier standards apply to off-road vehicles like heavy equipment, they are set by the EPA in the United States. Canadian standards are aligned to the US and use the same terminology. This standard measures engine exhaust emissions.

Stage – European Union standards that are harmonized to US EPA. This standard measures engine exhaust emissions at the tailpipe. (example: Stage V)

GHG – Green House Gas CO2 emissions standards set forth by NHSTA (National Highway Traffic Safety Administration). These standards are measures of the whole vehicle. Measurements within these standards may be improved my aerodynamics, transmission, and other improvements to overall operating efficiencies.

Major Milestones:

2007 – this was one of the most important years in diesel technology in North America since it is when we moved to ULSD (ultra low sulfur diesel) fuel with less than 15ppm sulphur content. This change allowed us to implement advanced diesel aftertreatment systems and reduce emissions.

2010 - the introduction of SCR (Selective Catalytic Reduction) with DEF injection systems to reduce NOx output.

* exact standards vary by engine size and jurisdiction; this chart demonstrates the order of magnitude of the improvements. Prior to Tier3/Stage IIIA HC was unregulated so actual emissions are unknown.