Regulations for Vessel Air Emissions: Criteria of an

PDF Version

RDIMS No.: 10425096
Date (Y-M-D): 2015-05-01

Ship Safety Bulletin

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This bulletin explains the meaning of “Identical Engine” as it applies to the Vessel Pollution and Dangerous Chemicals Regulations (the Regulations).


Nitrogen oxides (NOx) form when the air (which contains nitrogen), is drawn into an engine, mixes with the fuel, and ignites. Limiting how much NOx pollutants form requires adjusting the operation or design of a vessel’s engines. To address NOx exhaust emissions from shipping, the International Maritime Organization (IMO) through MARPOL, Annex VI, has developed a set of NOx emission standards for vessel engines, which are set out in the Regulations

Emissions Standards:  Nitrogen oxides

New engines, over 130 kilowatts, fitted onto vessels that operate in the North American Emission Control Area (NA-ECA) must meet NOx emission standards, except those used solely for emergency purposes, no matter the ship’s tonnage. These standards are divided into three different tier levels; ranging from the least stringent Tier I, to the most stringent, Tier III.

The Tier emission standards that apply to a new engine depend on the engine’s installation date:

  • Before January 1, 2016, engines fitted onto vessels in Canada must meet the Tier II NOx standards.
  • Effective January 1, 2016:
    • engines fitted on vessels operating in waters under Canadian jurisdiction south of Latitude 60oN will be required to meet Tier III NOx standards,
    • vessels operating north of 60oN, will continue to meet Tier II. 

Identical Engines Scenarios

Under the Regulations, if an “identical engine” replaces an existing marine engine; it can be subject to the NOx Tier emission limit of the existing engine. For example, a Tier I engine can be replaced by an identical Tier I engine, regardless of date of installation. 

Please note: If the original engine was installed before the NOx standards applied, the replacement engine must meet Tier I as a minimum standard.

Determining compliance: “Identical Engine” criteria

An “identical” engine, for the purposes of the Regulations, would be either one that:

  1. has the same model number and engine manufacturer as the existing engine; or
  2. meets the criteria set out in the following table:

Table 1: “Identical Engine” Specifications

Conditions Vessel Length
  less than 24 metres 24 metres or greater
Engine power rating Within + 10% of existing engine Within + 10% of existing engine
Engine displacement Within + 10% of existing engine

The following document is available for downloading or viewing:

Regulations for Vessel Air Emissions: Criteria of an “Identical Engine” (216 KB)

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Questions concerning this Bulletin should be addressed to:
1. Air Emissions

2. Nitrogen oxides

3. Regulations

4. Pollution Prevention

5. Compliance

Environmental Protection
Transport Canada
Marine Safety and Security
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