Chapter 1 of the revised MARPOL Annex II carries the five regulations that set the scope of the whole instrument. They are short, but every word earns its place. Regulation 1 defines the terms; Regulation 2 says which ships the Annex binds; Regulation 3 lists the discharges the Annex does not touch; Regulation 4 lets a flag State relax certain carriage requirements; and Regulation 5 lets a flag State accept an alternative that works at least as well as the prescribed one. The text in force is the revised Annex II adopted by the Marine Environment Protection Committee in Resolution MEPC.118(52) on 15 October 2004, deemed accepted on 1 July 2006 under the tacit-acceptance procedure of article 16(2)(f)(iii), and in force from 1 January 2007. That revision replaced the old A/B/C/D pollution categories with the X/Y/Z/OS scheme and rewrote the discharge regime that the rest of the MARPOL Convention Annex II depends on.
A chemical-tanker officer who treats Chapter 1 as boilerplate will eventually misclassify a cargo, log a discharge that the law never permitted, or argue an exemption that does not exist. The definitions are not background. They are the switch that decides whether a tank washing goes to a reception facility or over the side, whether the IBC Code certificate covers the parcel, and whether a port state control officer writes a deficiency. This article works through Regulations 1 to 5 at the level a surveyor, cargo engineer, or Designated Person needs, and shows how each definition feeds the rules that bite in service.
Regulation 1: definitions
Regulation 1 opens with the standard formula, “For the purposes of this Annex,” and then runs through the defined terms in numbered paragraphs. The revised text carries the definitions that the rest of Annex II leans on. Several of them are deceptively narrow, and the narrowness is the point: a term that means exactly one thing cannot be argued sideways during a survey or a casualty inquiry.
Noxious Liquid Substance
Regulation 1.10 is the keystone. A Noxious Liquid Substance “means any substance indicated in the Pollution Category column of chapter 17 or 18 of the International Bulk Chemical Code or provisionally assessed under the provisions of regulation 6.3 as falling into Category X, Y or Z.” Read it twice, because three things hide inside it.
First, an NLS is defined by reference to the IBC Code, not by chemistry. A substance is noxious because it appears in the Pollution Category column of IBC Code chapter 17 or chapter 18 with an X, Y or Z, or because Parties have provisionally assessed it under Regulation 6.3 pending a full evaluation. There is no free-standing list of “noxious” chemicals inside Annex II; the list lives in the Code. That is why an amendment to chapter 17 of the IBC Code can change what counts as an NLS without a word of Annex II changing.
Second, the NLS definition is a discharge-category definition. The substance is noxious precisely because it sits in Category X, Y or Z. The categories are set in Regulation 6.1, and they grade the hazard: Category X presents a major hazard and justifies prohibition of any discharge; Category Y presents a hazard and justifies a limit on the quality and quantity discharged; Category Z presents a minor hazard and justifies less stringent restrictions. So the moment a cargo is identified as an NLS, its discharge regime is already half decided. The definition and the categorization are two halves of the same lock.
Third, “Other Substances” sit outside the NLS definition by design. Regulation 6.1.4 defines OS as substances shown as OS in the pollution-category column of IBC Code chapter 18 that have been evaluated and found to fall outside X, Y and Z because they present no harm when discharged from tank-cleaning or deballasting operations. Regulation 6.1.4 then states that the discharge of bilge, ballast water, or other residues containing only Other Substances “shall not be subject to any requirements of the Annex.” An OS parcel is carried under the same certificate machinery, but its washings escape the discharge limits entirely. Confusing an OS cargo with a Category Z cargo is a common error that costs a ship either an unnecessary prewash or, worse, an unlawful discharge.
Liquid substances
Regulation 1.7 fixes what “liquid” means for the Annex: “liquid substances are those having a vapour pressure not exceeding 0.28 MPa absolute at a temperature of 37.8 degrees C.” That number is not arbitrary. It is the boundary that separates the liquid-chemicals regime of Annex II and the IBC Code from the liquefied-gas regime of the IGC Code. A product with a higher vapor pressure at 37.8 degrees C is a gas for carriage purposes and is regulated as such, which is why Regulation 5.3 has to make special provision for gas carriers that also carry NLS. The 0.28 MPa cut is the line between two whole bodies of construction rules.
Chemical tanker, NLS tanker, and the Code link
Annex II uses two ship-type terms, and the difference between them is examined at every renewal survey. Under Regulation 1.16.1, a “chemical tanker means a ship constructed or adapted for the carriage in bulk of any liquid product listed in chapter 17 of the International Bulk Chemical Code.” Under Regulation 1.16.2, an “NLS tanker means a ship constructed or adapted to carry a cargo of Noxious Liquid Substances in bulk and includes an oil tanker as defined in Annex I of the present Convention when certified to carry a cargo or part cargo of Noxious Liquid Substances in bulk.”
The practical reading is this. A chemical tanker is built to the full IBC Code and can carry the whole chapter 17 list. An NLS tanker is the broader administrative term: any ship certified to carry NLS in bulk, which includes a product tanker built to Annex I that has been certified to carry, say, a parcel of an easy Category Z chemical alongside its oil cargoes. Every chemical tanker is an NLS tanker; not every NLS tanker is a full chemical tanker. The certificate machinery follows the term. A chemical tanker built on or after 1 July 1986 carries an International Certificate of Fitness under the IBC Code, and that certificate is accepted as the MARPOL Annex II certificate. An older ship may instead hold a Certificate of Fitness under the Bulk Chemical Code, the BCH Code.
The vapor-pressure boundary and the build-date lines explain why the ship-type terms cannot be read casually. A product tanker certified to carry one Category Z chemical is an NLS tanker for that voyage and answers to Annex II for the tank holding it, but it is not a chemical tanker and does not carry the full IBC Code Certificate of Fitness; its NLS authority is recorded instead on its International Pollution Prevention Certificate for the Carriage of Noxious Liquid Substances in Bulk. A purpose-built chemical carrier holds the IBC Code Certificate of Fitness, which lists every chapter 17 product it may carry and serves as its Annex II certificate. The two documents are not interchangeable, and a PSC officer reads the ship type off the certificate before reading the cargo. Mixing up the terms on a port-entry declaration or a cargo nomination is the kind of error that delays a loading while the certificate file is checked.
That Code split is itself defined in Regulation 1. The “Bulk Chemical Code” (the BCH Code) is the Code for the Construction and Equipment of Ships carrying Dangerous Chemicals in Bulk, adopted by Resolution MEPC.20(22). The “International Bulk Chemical Code” (the IBC Code) is the International Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk, adopted by Resolution MEPC.19(22). The distinction matters in service: the IBC Code is mandatory for chemical tankers built on or after 1 July 1986, while the BCH Code remains the recommendatory regime for ships built before that date. A surveyor reading an old Certificate of Fitness needs to know which Code it answers to, because the construction and survival standards differ.
Residue and residue/water mixture
Two definitions govern what is left in the tank after discharge. Regulation 1.12 says “residue means any noxious liquid substance which remains for disposal.” Regulation 1.13 says “residue/water mixture means residue to which water has been added for any purpose (e.g. tank cleaning, ballasting or bilge slops).” The pairing is deliberate. The pure residue is the clingage and stripping shortfall left after the cargo pump has done its work; the residue/water mixture is what you get once you add wash water, ballast, or slops. The discharge regime of Regulation 13 treats the two differently, and the cargo tank washing procedures are written around moving residue into a residue/water mixture that can then be discharged, prewashed, or sent ashore depending on the category and the tank arrangement.
The residue limit is where the definitions meet the steel. For ships constructed on or after 1 January 2007, the maximum quantity of cargo residue permitted to remain in a tank and its associated piping after unloading is 75 liters for products in Categories X, Y and Z, the figure set in Regulation 12. “Associated piping” is itself defined in Regulation 1.2 as the pipeline from the suction point in a cargo tank to the shore connection used for unloading, including all the ship’s piping, pumps, and filters in open connection with the cargo unloading line. The residue limit therefore covers the whole stripping path, not just the tank bottom. The efficiency-of-stripping rules in the cargo tank arrangement requirements exist to keep that residue under 75 liters.
Clean ballast and segregated ballast
Regulation 1.3 carries both ballast terms, and operators mix them up at their peril. “Clean ballast means ballast water carried in a tank which, since it was last used to carry a cargo containing a substance in Category X, Y or Z, has been thoroughly cleaned and the residues resulting therefrom have been discharged and the tank emptied in accordance with the appropriate requirements of this Annex.” “Segregated ballast means ballast water introduced into a tank permanently allocated to the carriage of ballast or to the carriage of ballast or cargoes other than oil or Noxious Liquid Substances variously defined in the Annexes of the present Convention, and which is completely separated from the cargo and oil fuel system.”
The difference is the tank, not the water. Clean ballast lives in a cargo tank that has been cleaned of its X, Y or Z residues to the Annex standard. Segregated ballast lives in a dedicated ballast tank that never holds cargo and is structurally separate from both the cargo and fuel systems. Segregated ballast can be discharged anywhere without an Annex II discharge concern, because it has not touched cargo. Clean ballast can be discharged because the tank has been cleaned to standard, but the qualifier “in accordance with the appropriate requirements of this Annex” is doing real work: the ballast is clean only if the cleaning met the Regulation 13 prewash and stripping rules for the category last carried. Calling deballasting water “clean” without having met those rules is one of the more frequent PSC findings on older NLS tankers.
En route
Regulation 1.6 defines “en route” to mean “that the ship is under way at sea on a course or courses, including deviation from the shortest direct route, which as far as practicable for navigational purposes will cause any discharge to be spread over as great an area of the sea as is reasonable and practicable.” The phrase is not just “moving.” It carries an obligation to spread the discharge. A ship sitting at anchor is not en route; a ship steaming a straight line at the minimum speed is technically en route but may not be spreading the discharge as the definition wants. The discharge criteria of Regulation 13 require the ship to be en route at a speed of at least 7 knots for self-propelled ships, or at least 4 knots for ships that are not self-propelled, and the en-route definition is why a slow drift with the discharge concentrated in one patch will not satisfy the rule even if the ship is nominally moving. Those speeds are not in Regulation 1; they sit in Regulation 13, and the en-route definition is what gives them their purpose. The same Regulation 13 criteria require the discharge to be made below the waterline through the underwater discharge outlet, at a distance of not less than 12 nautical miles from the nearest land, in a depth of water of not less than 25 meters. Every one of those numbers reads back to a Regulation 1 definition: the 12 miles is measured from the “nearest land” baseline of Regulation 1.9, the speed satisfies “en route” of Regulation 1.6, and the 25-meter depth uses “depth of water,” which Regulation 1.5 fixes as the charted depth.
Nearest land
Regulation 1.9 defines “from the nearest land” to mean from the baseline of the territorial sea, established under international law, with one elaborate exception for the north-eastern coast of Australia, where the baseline is drawn through a list of latitude-longitude points to keep discharges clear of the Great Barrier Reef. The 12-mile minimum distance for at-sea discharge in Regulation 13 is measured from this baseline, not from the visible coastline. Off the Queensland coast the baseline is pushed well out to sea by the reef line, so a discharge that looks 12 miles from the nearest island can still be inside the prohibited zone. A navigator using a chart distance to the nearest dry land rather than to the defined baseline can put the ship in breach without realizing it.
Ship constructed
Regulation 1.14.1 defines “ship constructed” as “a ship the keel of which is laid or which is at a similar stage of construction,” and then adds the conversion rule: a ship converted to a chemical tanker, whatever its original build date, is treated as a chemical tanker constructed on the date the conversion began. “Similar stage of construction” is defined in turn as the stage at which construction identifiable with a specific ship begins and assembly of that ship has commenced comprising at least 50 tonnes or one per cent of the estimated mass of all structural material, whichever is less. The build date is not a nicety. It decides which residue limits apply (the 75-liter figure is for ships built on or after 1 January 2007), whether the IBC Code or the BCH Code governs (the 1 July 1986 line), and which exemptions under Regulation 4 are open. A surveyor establishes the construction date first, because almost every quantitative threshold in the Annex keys off it.
PPM, depth of water, anniversary date, and the housekeeping definitions
Several Regulation 1 definitions do less analytical work but still appear on certificates and in records, and getting them wrong creates a paper trail of small errors. Regulation 1.11 fixes “ppm” to mean “ml/m3,” milliliters per cubic meter, so that any concentration figure in the Annex or in an approved Procedures and Arrangements Manual reads in a single consistent unit. Regulation 1.5 sets “depth of water” as “the charted depth,” which is why the 25-meter minimum depth in the Regulation 13 discharge criteria is checked against the chart datum rather than the tide-corrected sounding of the moment. Regulation 1.1 defines “anniversary date” as the day and month of each year corresponding to the date of expiry of the International Pollution Prevention Certificate for the Carriage of Noxious Liquid Substances in Bulk, which is the anchor for the annual and intermediate survey windows. These are not the definitions that decide a discharge, but a surveyor who treats the anniversary date loosely or reads a sounded depth as the charted depth will eventually produce a survey or a discharge record that does not stand up.
The Antarctic area: a special area defined in Regulation 13, not Regulation 1
Annex II has one special area, and it is the Antarctic area, the sea south of latitude 60 degrees S. A point worth flagging for anyone working from a checklist that lists “special area” under the definitions: in the consolidated revised Annex II the Antarctic area is defined and the special-area discharge prohibition is set in Regulation 13 (the discharge regulation), not in the Regulation 1 definitions list. Regulation 13.8.1 states that “Antarctic area means the sea area south of latitude 60 degrees S,” and the surrounding text of Regulation 13 prohibits, within that area, any discharge into the sea of Noxious Liquid Substances or mixtures containing such substances. So the special-area concept for Annex II is real and absolute, but the practitioner should cite it to Regulation 13, not to Regulation 1. Annex II does not carry the long list of named special areas that Annex I and Annex V do; for NLS, the only special area is the Antarctic, and the rule there is a flat prohibition rather than a tightened discharge criterion.
Regulation 2: application
Regulation 2 is two sentences, and both decide jurisdiction. Paragraph 1 reads: “Unless expressly provided otherwise, the provisions of this Annex shall apply to all ships certified to carry Noxious Liquid Substances in bulk.” Paragraph 2 reads: “Where a cargo subject to the provisions of Annex I of the present Convention is carried in a cargo space of an NLS tanker, the appropriate requirements of Annex I of the present Convention shall also apply.”
The test in paragraph 1 is certification, not the cargo on board today. A ship certified to carry NLS in bulk is inside Annex II whether or not it has an NLS parcel loaded on a given voyage. That is why the certificate, not the manifest, is the document a PSC officer checks first. The words “in bulk” carry the load-bearing limitation. A ship carrying chemicals only in packaged form, drums, intermediate bulk containers, or tank containers on deck, is not certified to carry NLS in bulk and so is not an Annex II ship. Packaged harmful substances are regulated under MARPOL Annex III and the IMDG Code instead. The bulk-versus-packaged split runs straight back to the words “in bulk” in both Regulation 2.1 and the Regulation 1.10 NLS definition, and it is the cleanest way to explain to a junior officer why the same chemical is an Annex II problem in a cargo tank and an Annex III problem in a drum.
Paragraph 2 handles the combination carrier. An NLS tanker that is also an oil tanker under Annex I (the Regulation 1.16.2 definition expressly folds such ships into the NLS-tanker term) has to satisfy both Annexes when it carries an Annex I cargo in a cargo space. The two regimes stack; the ship does not get to pick the lighter one. A product/chemical carrier loading a gasoil parcel in one tank and a Category Z chemical in another answers to Annex I for the gasoil tank and Annex II for the chemical tank at the same time. The Oil Record Book covers the oil operations; the Cargo Record Book covers the NLS operations; both have to be right.
What Regulation 2 does not do is set the construction and equipment standard. It applies the Annex; the IBC Code (made mandatory through Regulation 11) sets the build standard for ships carrying chapter 17 products. The certification under the IBC Code and the application under Annex II are linked but distinct steps: the Code certifies the ship as fit to carry the listed chemicals, and Annex II then applies its pollution-prevention regime to that certified ship. Reading the two together is the everyday reality of a chemical-tanker certificate file.
Regulation 3: exceptions
Regulation 3 lifts the discharge requirements of the Annex in a closed list of cases. Its opening line is precise: “The discharge requirements of this Annex shall not apply to the discharge into the sea of Noxious Liquid Substances or mixtures containing such substances” in the three situations that follow. The word “requirements” matters. Regulation 3 does not say the discharge never happened or that no report is due; it says the discharge limits do not apply to it. The reporting and record-keeping obligations elsewhere in MARPOL still run.
The first exception, in Regulation 3.1, is a discharge “necessary for the purpose of securing the safety of a ship or saving life at sea.” This is the master’s override. If pumping a tank over the side is what it takes to keep the ship afloat or to save people, the discharge limits step back. The exception is about necessity, not convenience; the discharge has to be needed for safety or life, and a casualty inquiry will test whether a less polluting option was available.
The second exception, in Regulation 3.2, covers a discharge that “results from damage to a ship or its equipment.” This one carries two express conditions, and both have to hold. Under the first condition, “all reasonable precautions” must have been taken after the occurrence of the damage or the discovery of the discharge for the purpose of preventing or minimizing the discharge. Under the second, the fault bar, the exception is lost if “the owner or the master acted either with intent to cause damage, or recklessly and with knowledge that damage would probably result.” The fault bar is the same formula MARPOL uses across its annexes, and it is strict: intent or recklessness with knowledge of probable damage knocks out the defense. A discharge from a collision or grounding is excepted only if the crew did everything reasonable to limit it and nobody caused the casualty deliberately or recklessly.
The third exception, in Regulation 3.3, is the spill-combating discharge: a discharge “approved by the Administration, when being used for the purpose of combating specific pollution incidents in order to minimize the damage from pollution.” This covers the deliberate use of a substance to fight an existing spill, where dispersing a controlled quantity reduces the overall harm. It carries a second consent layer: “any such discharge shall be subject to the approval of any Government in whose jurisdiction it is contemplated the discharge will occur.” So a spill-combating discharge needs both the flag State’s approval in principle and the coastal State’s approval for the actual location. The double consent is what separates a lawful spill-response measure from an unlawful operational discharge dressed up as one.
These three exceptions are exhaustive. There is no general “force majeure” or “commercial necessity” exception in Annex II. A discharge that does not fit Regulation 3.1, 3.2, or 3.3 is judged against the full discharge criteria of Regulation 13, and a discharge outside those criteria is a contravention. The exceptions are narrow on purpose, because a wide reading would swallow the discharge regime.
Regulation 4: exemptions
Regulation 4 is where a flag State can relax certain carriage requirements for specific ships, mostly older ones, where strict application of an upgrade would be unreasonable or impracticable. It is longer and more conditional than Regulations 3 and 5 because each relaxation is hedged with reporting duties.
Paragraph 1 handles amendments to carriage requirements caused by upgrading the categorization of a substance. When an amendment to Annex II, the IBC Code, or the BCH Code involves changes to structure, equipment, or fittings because a substance has been moved to a stricter category, Regulation 4.1.1 lets the Administration “modify or delay for a specified period the application of such an amendment to ships constructed before the date of entry into force of the amendment, if the immediate application of such an amendment is considered unreasonable or impracticable.” The relaxation is determined substance by substance, not ship by ship. Regulation 4.1.2 then requires the flag State that grants a relaxation to report to IMO with the details of the ship or ships, the cargoes they are certified to carry, the trade each ship is engaged in, and the justification, for circulation to the other Parties. The exemption is reflected on the certificate. The vegetable-oil case in Regulation 4.1.3 is a worked example of the same logic: an NLS tanker certified to carry individually identified vegetable oils can be exempted from some carriage requirements provided it meets ship type 3 standards except for cargo tank location, with the cargo tanks protected by ballast spaces at the defined inboard distances (wing tanks placed so the cargo tanks are nowhere less than 760 mm inboard of the side shell, and double bottoms at not less than B/15 m or 2.0 m at the centerline, whichever is less, with a 1.0 m minimum). The point of the carve-out was to let ships keep carrying vegetable oils after the 2007 revision pulled those oils into the chemical-tanker regime.
Paragraphs 2 and 3 handle the restricted-voyage exemption for older ships. Subject to the conditions in paragraph 3, the prewash-and-procedures requirements of Regulation 12.1 need not apply to a ship constructed before 1 July 1986 engaged on restricted voyages between ports of one Party, or between ports of Parties, as determined by the Administration. Paragraph 3 then loads on the conditions: every time a tank that held a Category X, Y or Z substance is washed or ballasted, the tank is washed using an approved prewash procedure and the washings go to a reception facility; subsequent washings or ballast may go to a reception facility or to sea under the other provisions of the Annex; the adequacy of the reception facilities at those ports is approved by the Governments concerned; for voyages to other Parties’ ports the flag State notifies IMO of the exemption particulars for circulation; and the certificate is endorsed to show the ship is solely engaged on such restricted voyages. The exemption is real but tightly fenced, and the endorsement on the certificate is what tells a PSC officer the ship is allowed to operate this way.
Paragraph 4 is the ballast-free exemption. For a ship whose constructional and operational features are such that ballasting of cargo tanks is not required and cargo tank washing is only required for repair or dry-docking, the Administration may exempt it from the provisions of Regulation 12, provided the design, construction, and equipment are approved by the flag State for the service intended; any tank washings before repair or dry-docking go to an approved reception facility; the certificate records that each cargo tank is certified for a restricted number of compatible substances that can be carried alternately without intermediate cleaning, and records the exemption particulars; the ship carries an approved Procedures and Arrangements Manual; and, for voyages to other Parties’ ports, the flag State notifies IMO. This exemption fits a small number of dedicated ships that load and discharge a tight slate of compatible cargoes and never need to wash between parcels at sea.
The structure across all four paragraphs is the same: the flag State may grant relief, but only with conditions on the ground, an endorsement on the certificate, and, where the ship trades to other Parties, a report to IMO. None of these exemptions is self-executing, and none of them lets a ship discharge more than the Annex otherwise allows; they relax construction and procedural requirements, not discharge limits.
Regulation 5: equivalents
Regulation 5 is the flexibility valve for technology. Paragraph 1 reads: “The Administration may allow any fitting, material, appliance or apparatus to be fitted in a ship as an alternative to that required by this Annex if such fitting, material, appliance or apparatus is at least as effective as that required by this Annex.” The standard is “at least as effective.” A flag State cannot accept a cheaper option that does the job slightly worse; the alternative has to match or beat the prescribed one on effect.
Then comes the bar that practitioners most often miss. The same paragraph continues: “This authority of the Administration shall not extend to substitution of operational methods to effect the control of discharge of Noxious Liquid Substances as equivalent to those design and construction features which are prescribed by regulations in this Annex.” A flag State can accept a different piece of equipment that works as well as the required one. It cannot accept a procedure, a way of operating the ship, as a substitute for hardware the Annex requires. If Annex II prescribes a design or construction feature, an operational method does not count as an equivalent for it. This keeps the equivalents power from quietly hollowing out the construction standard: you cannot replace a required stripping system with a promise to strip carefully.
Paragraph 2 attaches the reporting duty: a flag State that allows an equivalent under paragraph 1 “shall communicate to the Organization for circulation to the Parties to the Convention particulars thereof, so that appropriate action may be taken.” As with Regulation 4, the relief is not private. IMO and the other Parties learn of each equivalent, which lets port States recognize it and lets the Committee spot any drift in what flag States are accepting.
Paragraph 3 is the gas-carrier equivalence. The construction and equipment of a liquefied-gas carrier certified to carry NLS listed in the applicable Gas Carrier Code are deemed equivalent to the construction and equipment requirements of Regulations 11 and 12, provided the ship holds a Certificate of Fitness under the appropriate Gas Carrier Code, holds an International Pollution Prevention Certificate for NLS in bulk limited to the NLS listed in that Code, has segregated ballast arrangements, has pumping and piping that keep the residue within the Regulation 12 limits, and carries an approved Manual ensuring no operational mixing of cargo residues and water and no residue left in the tank after the prescribed ventilation. This is the bridge between the gas-carrier regime and Annex II, and it is why a gas carrier occasionally carrying a few listed NLS does not have to be built twice.
How the definitions drive the operative rules
The five regulations of Chapter 1 are the gearing for the rest of Annex II. The NLS definition in Regulation 1.10 routes a cargo into Category X, Y or Z, and that category then sets the discharge regime in Regulation 13, the prewash trigger, the residue-limit obligation in Regulation 12, and the cargo tank washing procedure recorded in the Cargo Record Book. Change the IBC Code chapter 17 entry, and the cargo’s category, discharge regime, and required tank arrangement all move with it, without a word of Chapter 1 changing. That is the design: the definitions point outward to the Code and to the categories, so the operative rules update when the science updates.
The liquid-substance definition in Regulation 1.7 draws the line that keeps gases out of Annex II and explains why Regulation 5.3 has to make a special bridge for gas carriers. The residue and residue/water-mixture definitions in Regulations 1.12 and 1.13 set up the discharge arithmetic that the cargo tank arrangement requirements are built to satisfy, with the 75-liter residue ceiling for ships built on or after 1 January 2007 as the target the stripping system has to hit. The clean-ballast and segregated-ballast definitions decide whether deballasting water is an Annex II discharge at all. The en-route and nearest-land definitions, read with the Antarctic-area prohibition in Regulation 13, fix where and how a permitted discharge may happen.
Regulation 2 then aims all of this at the right ships: those certified to carry NLS in bulk, with the IBC Code certificate doing the construction certification and Annex II doing the pollution-prevention application, and with packaged chemicals handed off to Annex III. Regulation 3 carves out the genuine emergencies and the approved spill-response cases. Regulations 4 and 5 give the flag State controlled room to relax carriage requirements for specific older or special-purpose ships and to accept equivalent hardware, each hedged with an IMO report so the relief stays visible. A practitioner who holds these five regulations clearly will read the rest of Annex II as a set of consequences rather than a wall of disconnected rules.
Limitations
This article covers the text of Regulations 1 to 5 of the revised Annex II as adopted in Resolution MEPC.118(52) and in force from 1 January 2007. The Annex has been amended since, and individual definitions, thresholds, and cross-references can be updated by later MEPC resolutions; always check the current consolidated Annex II and the latest IBC Code edition for the operative wording on the day. The definitions summarized here are paraphrased and explained for working use, not reproduced verbatim in full; for any compliance decision, survey, or casualty matter, the controlling text is the official IMO consolidated Annex II, and the categorization that decides a cargo’s regime is the entry in the IBC Code chapter 17 or 18 pollution-category column, not any summary.
The article does not cover Regulation 6 (categorization detail and provisional assessment), the certification and survey regulations (Regulations 7 to 10), the construction and equipment regulations (Regulations 11 and 12), the discharge criteria in full (Regulation 13), the Procedures and Arrangements Manual (Regulation 14), the Cargo Record Book (Regulation 15), the measures of control by port States (the survey and control regulations), the marine pollution emergency plan (Regulation 17), or reception facilities (Regulation 18). Several of those are treated in their own articles. The residue figures, build-date lines, and Code resolution numbers quoted here are drawn from the MEPC.118(52) text and the IBC Code as adopted; a survey file should verify each against the certificate and the ship’s actual construction date before relying on it.