A chemical-tanker chartering desk fixes cargoes faster than the IMO reprints the IBC Code. A new specialty solvent, a reformulated biodiesel blend, a trade-named mixture whose exact recipe is a manufacturer’s secret: any of these can appear on a nomination years before it has a line in IBC Code Chapter 17. The treaty has to answer one question before that cargo can load. Is this substance lawful to carry, and under what regime? The answer comes from Regulation 6.3 of the revised MARPOL Annex II, the provisional-assessment route, read together with the procedural guidelines in MEPC.1/Circ.512/Rev.1.
A note on the regulation number is needed at the outset, because the title under which this topic is often filed does not match the consolidated treaty text. The revised Annex II, adopted by Resolution MEPC.118(52) on 15 October 2004 and in force since 1 January 2007, has no regulation titled “Other liquid substances.” In the consolidated text, Regulation 6 is “Categorization and listing of Noxious Liquid Substances and other substances,” and its paragraph 6.3 carries the provisional-assessment rule. Regulation 7, the next number, is “Survey and certification of chemical tankers,” and Regulation 8 is “Surveys.” So the machinery this article covers, carriage of a substance not yet categorized, is Regulation 6.3 of the Annex, supported by the IMO guidelines and the annual MEPC.2/Circular, not a standalone “Regulation 7.” The sibling article on Regulation 6 categorization sets out the X, Y, Z and OS taxonomy and the harm basis behind each band; this article goes deep on the institutional pipeline that gets an unlisted chemical a category in the first place and keeps the list current.
What Regulation 6.3 actually says
The text is short and the discipline it imposes is strict. Where it is proposed to carry in bulk a liquid substance that has not been categorized under Regulation 6.1, the governments of the parties to the Convention involved in the proposed operation must establish and agree on a provisional assessment of that operation, on the basis of the guidelines adopted under the Annex. Until full agreement among the governments involved is reached, the substance must not be carried. The bar is a hard one. No provisional category, no agreement, no carriage.
The notification duty follows. As soon as possible, but not later than 30 days after agreement is reached, the government of the producing or shipping country that initiated the agreement must notify the IMO and provide the details of the substance and its provisional assessment, for annual circulation to all parties for information. The IMO then maintains a register of all such provisionally assessed substances until they are formally included in the IBC Code. That register is the MEPC.2/Circular, treated below.
Read against the definition of a noxious liquid substance, the importance of 6.3 is plain. Regulation 6 ties the NLS definition to two sources: a product shown in the pollution-category column of IBC Code Chapter 17 or 18, or a product provisionally assessed under Regulation 6.3 as falling into Category X, Y or Z. An NLS is not “a substance in the Code.” It is a substance in the Code or one provisionally assessed under 6.3. That second limb is what lets the Annex regulate a cargo the day after its chemistry is first agreed, rather than the year the Code is next reprinted. Without 6.3 the Annex would have a gap the width of the print cycle, and chemical trade would either stall on every new product or move it ungoverned.
Why a provisional route exists at all
The IBC Code is not a living document in the sense a website is. It is a treaty instrument amended by MEPC and MSC resolution and then reprinted on a multi-year cycle. The revised IBC Code that accompanied the revised Annex II was adopted by Resolution MEPC.119(52) and by Resolution MSC.176(79) on 10 December 2004, both in force 1 January 2007, and the substantial product-list amendments that recast Chapters 17 and 18 entered force on 1 January 2021. Between those reprints the printed cargo list is frozen. Chemistry is not. New products reach the market continuously, and existing products get reformulated, reblended and renamed.
Two forces pull against the print cycle. One is the pace of the specialty-chemical and biofuel trades, where a product can go from pilot plant to a 5,000-tonne parcel inside a year. The other is the structure of the assessment itself, which is deliberately slow because it is data-driven. A full IMO categorization needs a GESAMP hazard profile built from toxicology and environmental-fate testing, and that testing takes time and money. The provisional route bridges the two. It lets the cargo move on a categorization the interested governments agree is sound on the data available, while the full assessment runs in parallel and the manufacturer assembles the complete data set.
The bridge is temporary by design. A tripartite agreement is valid for three years. The window is meant to give the manufacturer or shipper time to submit a full data set and for the IMO bodies to complete the formal evaluation. If the product is worth trading, the data arrives and the entry graduates to a permanent listing. If it is not, the agreement lapses and the provisional entry drops out of the next circular. The three-year clock is the mechanism that keeps the provisional register from silting up with abandoned products.
The tripartite agreement: who the three parties are
The word “tripartite” names the three categories of government that an agreement can involve, and MEPC.1/Circ.512/Rev.1 defines each role precisely. The reporting country is the country that, through its Administration, undertakes the provisional assessment of a product in accordance with the guidelines and establishes the tripartite agreement. It is usually the producing or shipping State, the one whose industry wants to move the cargo. The receiving country is the country or countries that will be the recipient of the product covered by the assessment. The participating countries are those that have concurred and signed on to the agreement proposed by the reporting country, and they include the flag State or States of the vessels that would carry the product as well as the recipient countries.
So the three parties are the producer or shipper, the receiver, and the flag of the carrying ship, with the reporting country acting as the assessor and initiator. The flag State’s place in the agreement matters operationally. A chemical tanker can only carry a provisionally assessed product if its flag is a party to the agreement covering that product. A Panama-flagged tanker chartered to lift a tripartite-agreement cargo needs Panama to be a participating country in that specific agreement, or the carriage is not lawful under the Annex. This is the point at which the abstract provisional category meets the concrete flag-State certification of the ship that will actually load it.
A practical consequence flows from the named-countries structure. A tripartite-agreement entry in the MEPC.2/Circular is not open to all comers. It names the specific countries that may produce, receive and carry the product. An owner whose flag is not on the list, or a receiver whose State is not a party, cannot simply rely on the entry; they have to join the existing agreement first. The guidelines set out the joining route: an interested party checks the IMO website for an existing agreement, contacts the reporting country directly, and once the reporting country confirms it, the interested party is added. The agreement widens by accretion, country by country, until the product is fully assessed and the named-country limit disappears.
Establishing an agreement when none exists
When there is no tripartite agreement for a product, the guidelines require one to be established before the product moves, because a product that appears neither in the IBC Code nor in the latest MEPC.2/Circular cannot be carried other than under a tripartite agreement with an expiry date. The first step for the reporting country’s Administration is to consult the latest GESAMP Composite List to see whether the product, or its components, already carry a GESAMP Hazard Profile. If a profile exists, the Administration can provisionally assess the product against it and assign a category. If no profile exists, a provisional hazard profile has to be provided by the manufacturer or shipper as a starting point, pending the formal GESAMP evaluation.
The assessment the reporting country performs is not freehand. It applies the same MARPOL Annex II categorization criteria and the same IBC Code carriage criteria, set out in Chapter 21 of the Code, that the IMO uses for a permanent assessment. The provisional category is meant to land where the permanent category will land. The whole point of the three-year window is that the provisional answer should hold up when the full data set arrives, so the reporting country does the assessment to the published standard rather than guessing. Where it cannot, because the data are thin, the conservative reading governs: an unresolved hazard is treated as present, not absent.
The MEPC.2/Circular: the live supplement to the Code
The IMO Secretariat collects the provisional assessments and tripartite agreements reported under Regulation 6.3 and publishes them annually as the MEPC.2/Circular, “Provisional Categorization of Liquid Substances in accordance with MARPOL Annex II and the IBC Code.” The circular is issued each December, and each issue incorporates the new products assessed and the modifications made to existing products during the year. The series is sequential and each issue supersedes the last: MEPC.2/Circ.29 in December 2023, MEPC.2/Circ.30 in December 2024, MEPC.2/Circ.31 in December 2025. An officer treats the current circular as a live supplement to the IBC Code. A cargo absent from the printed Chapter 17 may be perfectly lawful to carry because it sits in this year’s circular.
The circular is not a single flat list. It is built from numbered lists that sort products by how they were assessed and what they are. List 1 holds pure or technically pure products and generic mixtures evaluated as a whole. List 2 holds pollutant-only mixtures that contain at least 99 percent by weight of components already assessed by the IMO. List 3 holds trade-named mixtures that present safety hazards. List 4 holds pollutant-only mixtures that contain one or more components, each forming more than 1 percent by weight of the mixture, which have not yet been assessed by the IMO. List 5 holds substances not shipped in pure form but only as components in mixtures. The list a product sits in tells an officer immediately what kind of entry it is and how settled its category is.
The expiry-date column is the single most consequential field in the circular for an operator. An entry established under a tripartite agreement carries an expiry date and names the countries party to it. An entry that has been fully assessed by the IMO carries no expiry date and is valid for all countries. The difference is the difference between a provisional cargo, country-limited and time-limited, and a settled one. Products in List 1 that have been formally reviewed by the ESPH and are valid for all countries will be incorporated into the IBC Code when the Code is next updated, which closes the loop between the circular and the printed Code.
The graduation path: from country-limited to printed line
The full life of a new product runs along a clear path, and naming each stage explains the document trail an officer follows. A product enters as a tripartite-agreement entry: country-limited, with an expiry date, sitting in List 1 or one of the mixture lists. While the agreement runs, the manufacturer assembles the full data set and submits the product for formal IMO evaluation. When the ESPH completes its review and the category and carriage requirements are confirmed, the product moves to an all-countries, no-expiry entry in the circular, replacing the tripartite agreement. At the next revision of the IBC Code, the all-countries entry is folded into Chapter 17, 18 or 19 as a printed line, and it drops out of the circular because the Code now carries it.
That is the entire journey: a country-limited provisional entry with an expiry date, then an all-countries permanent circular entry with no expiry, then a printed Chapter 17, 18 or 19 line. Regulation 6.3 makes the front end of the journey lawful; the GESAMP and ESPH machinery moves the product along it; the IBC Code revision finishes it. An officer reading a category off the circular rather than the Code is reading a cargo that is somewhere on that journey, and the expiry-date field tells them where.
IBC Code Chapters 17, 18, 19 and 21: where the destination lives
The destination of an assessed product is one of three IBC Code chapters, and a fourth chapter holds the criteria. Chapter 17 is the summary of minimum requirements for products that are carried as noxious liquid substances or that present a safety hazard; each entry shows the product name, its pollution category in the appropriate column, its ship type, and the tank, environmental-control and special-requirement columns. Chapter 18 is the list of products to which the Code does not apply, the OS substances and other cargoes that fall outside the NLS discharge restriction but that the Code still names so they can be identified. Chapter 19 is the index of products carried in bulk, the cross-reference that ties product names and synonyms to their Chapter 17 or 18 entries. Chapter 21 is the one an assessor uses rather than reads off: it carries the criteria for assigning carriage requirements to a product, the ruleset the ESPH applies when it turns a hazard profile into a ship type and a set of column entries.
The 1 January 2021 amendments to the IBC Code, adopted to align it with the revised hazard data, moved a number of products between chapters. Several cargoes that had sat in Chapter 18, the list of products to which the Code does not apply, were reassessed and moved into Chapter 17, which means they can no longer be carried on tankers that do not hold a Certificate of Fitness. That migration is the visible end of the assessment pipeline: a product’s environmental-fate data changed its category, the category changed its chapter, and the chapter changed which ships may carry it. The provisional route is the front end of the same pipeline, where a new product first gets the category that will eventually decide its chapter.
The chapter a product lands in is the difference between a cargo any suitable tanker can carry and one that needs a chemical tanker with a Certificate of Fitness and the matching ship type. A Chapter 18 product carries no Annex II discharge restriction. A Chapter 17 product carries its category, its ship type, and the Regulation 13 discharge and prewash regime that the category triggers. So the question the provisional assessment answers, what category does this new product get, is the question that decides whether a given ship can lift it at all.
The biofuel trade is the clearest current case of the pipeline under load. A fatty-acid methyl ester or a hydrotreated vegetable oil is assessed through the same GESAMP and ESPH route as any other liquid, given a category, and listed or provisionally categorized like any other product. Blends of a mineral product and a biofuel raise the trade-name-versus-composition problem at its sharpest, because the category of the blend depends on the blend ratio and may differ from either component. A FAME-and-gas-oil blend changes character as the ratio shifts, and the category that governs its discharge has to track the actual composition loaded, not the nominal product name on the fixture. That is exactly the situation the provisional-assessment route and the mixture lists in the circular are built to handle, which is why the biofuel slate leans heavily on the circular rather than on the printed Code. The growth of bunkers and blends since the introduction of the marine-fuel sustainability rules has pushed a steady stream of new blend entries through the assessment machinery.
The GESAMP hazard profile behind the provisional category
No category, provisional or permanent, is assigned by judgment alone. Each rests on a GESAMP hazard profile, the output of the Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection, working through its Working Group on the Evaluation of the Hazards of Harmful Substances Carried by Ships, the GESAMP/EHS Working Group. The group evaluates the toxicological and environmental-fate data for a substance and issues a hazard profile that rates it across lettered columns. The procedure is published as GESAMP Reports and Studies No. 64, “The Revised GESAMP Hazard Evaluation Procedure for Chemical Substances Carried by Ships,” which superseded the earlier 2002 procedure and is the technical reference the whole system runs on.
The profile groups its columns into families. The A and B columns describe the aquatic environment: A1 is bioaccumulation, A2 is biodegradation, B1 is acute aquatic toxicity, and B2 is chronic aquatic toxicity. The C and D columns describe mammalian and human health, covering acute oral, dermal and inhalation toxicity, skin and eye effects, and long-term health effects. The E column describes other effects, including tainting of seafood, physical behavior such as floating or sinking, and interference with the use of coastal amenities. The full A-to-E profile is what the IBC Code needs to set every carriage requirement. To set only a pollution category, the minimum set is A1 bioaccumulation, A2 biodegradation and B1 acute aquatic toxicity, and a profile reduced to those three columns carries a footnote that it cannot be used for any other purpose. The detailed mapping from the column ratings to Category X, Y, Z or OS is covered in the Regulation 6 categorization article; the point here is that the same profile drives both the provisional and the permanent category.
The GESAMP Composite List and the PPR.1/Circular
The running record of every substance the GESAMP/EHS has profiled is the GESAMP Composite List of Hazard Profiles. It is the single working dataset behind both the IBC Code and the MEPC.2/Circular, and it is updated once a year. The source for the latest composite list is the PPR.1/Circular, which contains a compilation of all substances assessed by GESAMP/EHS and the resulting GESAMP Hazard Profiles, issued after the group’s annual meeting along with the report of that meeting. A reporting country’s Administration consults the current composite list as the first step of any provisional assessment, because if the product or its components already carry a profile, the assessment is a matter of applying the published criteria rather than commissioning new science.
The cost and the cadence of the GESAMP step explain why the provisional route is needed. A GESAMP/EHS assessment is fee-based, and the group meets annually rather than continuously, so a substance newly submitted for profiling can wait the better part of a year for its turn and longer for the full evaluation to conclude. A manufacturer who wants to ship before that clock runs out uses the tripartite route to move the cargo on the data available, while the formal profiling proceeds in the background. The provisional and the permanent tracks run in parallel, fed by the same composite list, and they converge when the permanent assessment is done.
Submitting a new product for permanent assessment
The provisional route is a bridge; the permanent assessment is the destination. The path to a permanent listing runs through two bodies in sequence, and the division of labor between them is the structure of the whole system. First, the product or the components of the mixture are assessed by the GESAMP/EHS Working Group and assigned a GESAMP Hazard Profile, which establishes the environmental hazard of the substance and adds it to the composite list. Second, the manufacturer makes a request through a national Administration to submit the product for evaluation by the IMO, using the PPR Product Data Reporting Form.
The reporting form is the formal document that moves a product through the pipeline. It sets out all the technical information the ESPH needs to assign a pollution category under MARPOL Annex II and carriage conditions under the IBC Code, and the manufacturer proposes, where possible, a pollution category, a ship type and carriage requirements for the product. The form and its guidance notes are set out in MEPC.1/Circ.857. The Administration submits the completed form to the IMO, and the evaluation is undertaken by the ESPH Working Group, the Evaluation of Safety and Pollution Hazards group, which reports to the Sub-Committee on Pollution Prevention and Response, the PPR Sub-Committee. The PPR Sub-Committee replaced the former Bulk Liquids and Gases Sub-Committee, the BLG Sub-Committee, in the 2014 reorganization of the IMO’s sub-committee structure, so older references to “the BLG working group” and current references to “the PPR ESPH group” name the same line of work at different dates.
The role split is the thing to hold onto. GESAMP/EHS settles the science, producing the hazard profile and maintaining the composite list. The ESPH, under PPR, settles the regulation, applying the Annex II and IBC Code Chapter 21 criteria to that profile and assigning the category, ship type and carriage requirements. The MEPC adopts the result, the Secretariat publishes it in the MEPC.2/Circular, and the IBC Code revision eventually prints it. A submission for a new cargo enters the pipeline at the GESAMP/EHS end and exits, on the order of two to three years later for a full assessment, as a permanent entry. The tripartite agreement is the interim instrument that lets the cargo move while the pipeline runs, which is why the three-year tripartite validity is matched to the time a full assessment takes.
Mixtures, blends, and the trade-name problem
The provisional route exists in its sharpest form for mixtures, because a mixture is exactly the kind of product the printed Code struggles to keep up with. The MEPC.2/Circular’s list structure is built around the mixture problem. A pollutant-only mixture that contains at least 99 percent by weight of components the IMO has already assessed can be handled with a light touch, because the assessed components already carry profiles. A pollutant-only mixture that contains one or more unassessed components, each forming more than 1 percent by weight, needs more work, because the unassessed fraction has to be evaluated before the blend’s category is sound. The 1 percent threshold is the dividing line. A product can still be shipped as an assessed product if it contains up to a total of 1 percent unassessed components, provided those components are not oil as defined in MARPOL Annex I and are not mixed with a product whose pollution category is OS.
The n.o.s. generic entry is the mechanism that lets many blends move without a bespoke addendum to the Code. Where the components of a mixture are largely assessed, the mixture can be shipped under the applicable generic entry in the IBC Code, “Noxious Liquid (n.o.s.)” covered under Chapter 17 or “Non-Noxious Liquid (n.o.s.)” covered under Chapter 18, without the need to add the specific mixture to the Code. The generic entry carries a category appropriate to the worst-case the components allow, and the specific blend is recorded in the circular rather than the Code. This is the routine path for the many small-volume, frequently reformulated blends that would otherwise swamp the assessment pipeline.
The trade-name problem sits underneath all of this. The IBC Code and the circular key on chemical names and assessed compositions, but a cargo is sold under a trade name, and a single trade name can cover a mixture whose category depends on its exact recipe. The category attaches to the substance as assessed, not to the marketing label on the parcel. Confirming the category therefore means matching the trade name back to the assessed chemical name or to the right mixture list in the circular, not reading the label and assuming. A wrong match is not a paperwork slip; it can put a Category Y residue through a Category Z discharge plan. The mixture lists in the MEPC.2/Circular exist precisely so that a trade-named blend can be traced to its assessed category, which is why an officer handling an unlisted blend works from the circular rather than from the printed Code alone.
Reading the chain on board
The whole apparatus reaches the deck as a sequence of checks before a parcel of an unfamiliar product loads. The first check is whether the product is in the IBC Code at all. If it is, the category, ship type and carriage requirements come straight off its Chapter 17 or 18 entry, and the provisional machinery does not bear on it. If it is not in the Code, the second check is the current MEPC.2/Circular. A product found there carries a provisional or permanent category and the carriage conditions agreed for it, and the officer reads those just as they would a Chapter 17 line.
The third check, for a product found in the circular under a tripartite agreement, is the expiry date and the named countries. The agreement is only good while it has not expired, and it only covers the countries that are party to it, which must include the carrying ship’s flag. A tanker whose flag is not a participating country cannot lift the cargo on that agreement, however suitable the ship is in every other respect. The fourth check is the one that has no shortcut: matching the trade name on the nomination to the assessed product in the circular, because the category travels with the assessed composition and not with the marketing name.
When a product is in none of those places, neither the Code nor the current circular, the answer is that it cannot be carried yet. A tripartite agreement has to be established first, through the reporting country’s Administration, and the substance must not move until the governments involved reach full agreement. This is where the chartering desk’s pace collides with the treaty’s discipline. The provisional route is fast by the standards of treaty amendment, but it is not instant, and a fixture on a genuinely new product has to allow time for the assessment and the agreement before the ship can load. An officer who finds a nominated cargo in none of the authoritative sources has found a carriage that is not yet lawful, not a paperwork gap to be papered over.
How the provisional route ties into the rest of Annex II
The provisional category, once agreed, propagates through the Annex exactly as a permanent category does, because the Annex does not distinguish between them once the category is set. A provisionally assessed Category X, Y or Z substance is a noxious liquid substance for every purpose of the Annex. It triggers the Regulation 13 discharge controls and the prewash duty that its category requires. Its operations are logged in the Cargo Record Book under Regulation 15. The ship that carries it must meet the IBC Code ship type that its category and full hazard profile demand, which sets the cargo-tank arrangement under Regulation 11 and the pumping and stripping standard under Regulation 12. The provisional category is not a lesser thing than a printed one; it is the same regulatory object reached by a faster route.
The certification chain reaches the provisional cargo too. A chemical tanker carrying NLS in bulk holds an International Certificate of Fitness under the IBC Code, which covers its Annex II compliance, and the certificate lists the products the ship is approved to carry. For a tripartite-agreement cargo, the chain runs through the flag State: the flag must be a party to the agreement, and the ship’s ship type and arrangement must match what the provisional category and profile demand. The survey-and-certification framework that issues that certificate sits in Regulation 7, “Survey and certification of chemical tankers,” and Regulation 8, “Surveys,” of the revised Annex, which is the actual subject of the regulation numbers that this topic is sometimes mis-filed under. The carriage of a provisionally assessed substance is governed by Regulation 6.3; the certification of the ship that carries it is governed by Regulations 7 and 8.
Enforcement closes the loop. A port-State control officer inspecting a chemical tanker checks the cargoes on board against the ship’s Certificate of Fitness and against the current authoritative source for each cargo’s category, the IBC Code for a listed product and the MEPC.2/Circular for a provisional one. For a tripartite-agreement cargo the officer can check that the agreement is current, that the flag is a party, and that the carriage conditions match the entry. The provisional category that a reporting country agreed and the IMO circulated is, at the last step, the thing the inspection verifies, exactly as a printed category would be. The wider treaty frame is the MARPOL Convention itself, with Annex II as the chemical-pollution annex, and the provisional-assessment route is the part of that annex that keeps it from falling behind the trade it governs.
The companion mechanisms: IGC Code and cleaning additives
Two adjacent mechanisms use the same provisional logic, and naming them keeps the boundary of this article clear. Liquefied gases carried in bulk are governed by the IGC Code rather than the IBC Code, and the IGC Code has its own provisional-assessment arrangement for gases not yet listed, parallel to the Regulation 6.3 route for liquids. MEPC.1/Circ.512/Rev.1 references tripartite agreements established under the IGC Code provisions as well, and the annual circular carries gas-fuel entries in its later annexes, but the substantive rule for a liquid NLS is the Annex II one.
Tank-cleaning additives are the other adjacent case. A cleaning agent dosed into a prewash ends up in the marine environment with the wash water, so its components are assessed for pollution potential before the product may be used in a way that ends up discharged. The assessment uses the shortened GESAMP hazard profile, the same A1, A2 and B1 minimum set used to fix a pollution category, flagged so the profile is used only for evaluating cleaning additives and not for mixture calculations on bulk shipments. The additive case shows the same categorization logic applied to a substance that never appears on a cargo nomination, and it runs through the same GESAMP machinery, which is why the provisional and additive routes share a procedure even though they serve different purposes. The detailed treatment of additives sits with the Regulation 6 categorization article; the point here is that the GESAMP profile, not the Chapter 17 list, is the common foundation.
Limitations
This article describes the provisional-assessment and listing machinery, not the operational rules that flow from a category once it is set. The at-sea discharge conditions, the prewash end point, the slop-tank handling and the Cargo Record Book entry codes are the subject of Regulation 13 and its companion regulations, covered in the Regulation 13 cargo-tank-washing article. The X, Y, Z and OS taxonomy and the column-by-column mapping from a GESAMP profile to a category are covered in the Regulation 6 categorization article; they are summarized here only far enough to show how the provisional route reaches a category.
The regulation numbering needs a final caution. The consolidated revised Annex II adopted by MEPC.118(52) places the provisional-assessment rule in Regulation 6.3, places survey and certification of chemical tankers in Regulation 7, and surveys in Regulation 8. A document that refers to “Regulation 7 other liquid substances” is not using the consolidated Annex II numbering, and the substance of the provisional route is Regulation 6.3 read with MEPC.1/Circ.512/Rev.1. Any reference to the pre-2007 Category A, B, C, D system, to “Appendix III substances,” or to the original regulation numbers is pre-revision language; the consolidated text in force since 1 January 2007 speaks only of X, Y, Z and OS and the regulation numbers given here.
The category of a specific cargo must always be confirmed against the current authoritative source for that cargo, not inferred from a general description. For a listed substance that is the IBC Code Chapter 17, 18 or 19 entry under the assessed chemical name; for an unlisted or provisionally assessed substance it is the current MEPC.2/Circular, with the expiry date and named-countries fields read in full. Trade names, mixtures and blends do not carry their category on their label, and a mismatch between the marketed name and the assessed chemical or composition is a known source of error. The list numbers, the 1 percent unassessed-component threshold, the three-year validity and the 30-day notification period quoted here are the figures in the current guidelines and Annex text; treat them as a guide to the structure of the rule and verify the current figure against the consolidated Annex II, MEPC.1/Circ.512/Rev.1 and the latest MEPC.2/Circular before relying on it operationally. A provisional category is a finding on the data agreed at the time; it can change when the full assessment is complete, and an agreement can lapse if the data set is never submitted.
See also
- MARPOL Annex II: control of pollution by noxious liquid substances
- MARPOL Annex II Regulation 6: NLS categorization (X/Y/Z/OS)
- MARPOL Annex II Regulation 13: cargo-tank washing and discharge
- MARPOL Annex II Regulation 11: cargo-tank arrangement
- IBC Code: construction and equipment of chemical tankers
- IGC Code: gas carriers
- Chemical tanker: types and carriage requirements
- MARPOL Convention: the pollution-prevention treaty
- Port-State control