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Advise

Talk to us before the scope is fixed. We tell you which rules apply to your engine and project, and what the test and the documents must contain.

Examples of what we help withIMO legislationNOx Technical Code 2008MEPC resolutions we work withEPA legislationMentoring and educationThe rules we work with

Advise

Examples of what we help with

The questions vary from project to project.

It is the cheapest point to get it right.

Typical questions

These are examples. Tell us about your engine, your project and your deadline, and we tell you which rules apply.

  • Does my modification count as a substantial modification under MEPC.398(83)?
  • Amendment or new Technical File?
  • Do the EPA rules apply, and how do they combine with IMO?
  • Can a measured methane slip value replace the default under FuelEU Maritime?

Before the scope is fixed

The earlier we are involved, the easier it is to plan the test and the documents so they fit the rules.

  • Rules that apply to your engine and project
  • What the test must contain
  • What the documents must contain

Discuss your project

Advise

IMO legislation

MARPOL Annex VI and NTC 2008.

Two texts matter most for an engine project: MARPOL Annex VI, which sets the limits, and the NOx Technical Code 2008, which is mandatory under it and describes how an engine is certified and how compliance is shown.

MARPOL Annex VI

Regulation 13 of MARPOL Annex VI sets the NOx Tier requirements. The revised Annex VI was adopted in 2008 as MEPC.176(58).

  • Tier requirements in regulation 13
  • Revised Annex VI: MEPC.176(58)

NOx Technical Code 2008

The code sets mandatory procedures for testing, survey and certification of marine diesel engines, on a test bed and onboard. It was adopted as MEPC.177(58) in 2008 and has been amended since.

  • Technical File and EIAPP
  • Test bed and onboard procedures
  • Test plan agreed before the test
Read moreThe NOx Technical Code 2008 in detailThe MEPC resolutions we work with
Official sources

Advise

NOx Technical Code 2008

The method behind every certificate.

These are the parts of the code we work with most.

Surveys and certification

Chapter 2 covers surveys and certification, including the procedures for pre-certification of an engine.

  • Surveys and certification
  • Pre-certification of an engine (2.2)

Engine family and engine group

Chapter 4 sets the engine family and engine group concepts for serially manufactured engines. A parent engine represents the group.

Test bed measurements

Chapter 5 sets the procedures for NOx emission measurements on a test bed.

  • Procedures for NOx measurement on a test bed
  • Test report (section 5.10)

Compliance onboard

Chapter 6 gives the procedures for demonstrating compliance with the NOx limits onboard, with three methods.

  • Engine parameter check method (6.2)
  • Simplified measurement method (6.3)
  • Direct measurement and monitoring method (6.4)

Existing engines

Chapter 7 covers certification of an existing engine, the route added by MEPC.398(83).

See examplesTurbocharger cut-out on a two-stroke engine, documented for EPAVIT conversion of auxiliary engines
Read moreCalibration following Appendix 4

Advise

MEPC resolutions we work with

The IMO texts we meet most often in engine projects.

Each one links to the page where we use it.

MEPC.398(83)

Amendments to the NOx Technical Code 2008 on the certification of an engine subject to substantial modification, or certified to a Tier it did not hold at installation. In force since 1 September 2026.

MEPC.397(83)

Amendments to the NOx Technical Code 2008 on the use of multiple engine operational profiles for a marine diesel engine, including clarifying engine test cycles.

  • Adopted 11 April 2025

MEPC.399(83)

The 2025 Guidelines on Selective Catalytic Reduction (SCR) systems. They replace the 2017 guidelines, MEPC.291(71).

MEPC.414(84)

The 2026 guidelines for test-bed and onboard measurements of methane (CH4) and/or nitrous oxide (N2O) from marine diesel engines. They replace MEPC.402(83).

MEPC.1/Circ.854

Guidance on the application of regulation 13 of MARPOL Annex VI Tier III requirements to dual fuel and gas-fuelled engines.

  • Issued 1 July 2015

Replacement engines and approved methods

MEPC.230(65) gives guidelines for non-identical replacement engines not required to meet the Tier III limit (regulation 13.2.2). MEPC.243(66) gives guidelines on the approved method process (regulation 13.7.1).

  • MEPC.230(65), adopted 17 May 2013
  • MEPC.243(66), adopted 4 April 2014
Read moreA substantial modification only holds up if the emissions can be provenFrom methane measurement to a Statement of emission values

Advise

EPA legislation

EPA requirements and test procedures.

Where the trade requires it, we work to the EPA rules for marine engines.

Marine engines: 40 CFR Part 1042

Part 1042 sets the emission standards and requirements for marine compression-ignition engines. For large engines, Category 3, section 1042.104 gives the NOx standards by tier.

  • NOx standards for Category 3 engines (1042.104)
  • Other requirements, for example crankcase emissions (1042.115)
  • Requirements for vessel manufacturers, owners and operators (1042.660)

Test procedures: 40 CFR Part 1065

Part 1065 sets the engine-testing procedures, including the approval of alternate procedures.

  • Engine-testing procedures in Part 1065
  • Approval of alternate procedures (1065.12)
  • Combining IMO and EPA testing

Certification and changes

Section 1042.225 covers amending an application for certification, and 1068.50 sets the requirements for adjustable parameters. For engines with SCR, 1042.110 covers recording of reductant use and other diagnostic functions.

  • Amending applications for certification (1042.225)
  • Adjustable parameters (1068.50)
  • Reductant use and diagnostics for SCR (1042.110)
Map of the North American Emission Control Area along the Pacific, Atlantic and Gulf coasts and HawaiiNorth American ECA | NOx Tier III area
See an exampleTurbocharger cut-out on a two-stroke engine, documented for EPA
Official sources

Advise

Mentoring and education

Build the competence in your team.

Build the competence in your team

We train new members of your team in emission principles, practical emission measurement, advice on the rules and the certification process.

  • Emission principles
  • Practical emission measurement
  • Advice on the rules
  • The certification process
Training new colleagues around an engine and a touch table in a ship bridgeMentoring and education | Training new colleagues

Advise

The rules we work with

Grounded in the official regulations.

Grounded in the official regulations

We work directly from the regulations themselves, not from summaries. These are the regulations that matter most for marine engine emissions, certification and reporting.

  • Official texts, not summaries
  • The list is not complete: other rules can apply, depending on your engine, flag and class
Official sources

IMO

European Union

United States (EPA)

International standards

Unsure what the rules require?

Talk to us before the scope is fixed. It is the cheapest point to get it right.

Contact us