A Container That Wasn’t There

In March 2025, the container ship Solong collided with the anchored tanker Stena Immaculate in the North Sea off the East Yorkshire coast. Within hours, shipping media were reporting that the Solong was carrying fifteen containers of sodium cyanide. Fires broke out on both vessels, one crew member went missing, and for a tense stretch the story was as much about a toxic chemical release as it was about a collision.

The operator’s clarification came the next day: there was no laden sodium cyanide cargo aboard. What the vessel did have were four empty, uncleaned containers that had previously carried the chemical — still being monitored, but not the live hazard the early reporting suggested.

For most of the public, that was the end of the story. For anyone who classifies dangerous goods for a living, it’s the more interesting part. An empty uncleaned Class 6.1 container isn’t nothing — under IMDG Code it typically retains its dangerous goods status until cleaned, and that distinction between “empty uncleaned” and “harmless” is exactly the kind of nuance that gets lost between a shipping line’s press statement and a news wire. It’s also a useful entry point into a compliance layer most DG officers rarely think about: the International Cyanide Management Code, sitting quietly on top of the mandatory IMDG framework every time sodium or potassium cyanide moves by sea.

What the Cyanide Code Actually Is

The International Cyanide Management Code — usually just “the Cyanide Code” — is a voluntary, audit-based certification program launched in 2002 following a string of cyanide-handling incidents at gold mines, most notably the January 2000 tailings dam failure at Baia Mare, Romania. It was developed under a multi-stakeholder process involving gold producers, cyanide manufacturers, transport companies, UNEP, and the World Bank, and it’s administered today by the International Cyanide Management Institute (ICMI), based in Washington, DC.

As of ICMI’s most recent quarterly newsletter (Q1 2026), the program counts over 225 signatory companies and more than 320 currently certified operations, out of nearly 500 certified in total since the program began in 2006. Signatories commit to nine principles spanning production, transport, handling and storage, operations, decommissioning, worker safety, emergency response, training, and communication — each backed by published Standards of Practice and verified through independent third-party audits, with results posted publicly on ICMI’s website.

Critically, the Code isn’t limited to mine sites. It covers the full chain: cyanide manufacturers, the trucking and shipping companies that move it, and the mines that consume it — each evaluated against its own dedicated Verification Protocol.

UN 1689 Under IMDG Amendment 42-24: The Baseline Everyone Already Knows

None of this replaces the mandatory framework. Solid sodium cyanide ships as UN 1689, Class 6.1, Packing Group I, carrying a marine pollutant designation, per the current Amendment 42-24 Dangerous Goods List.

That classification triggers everything a DG officer would expect: UN-tested packagings rated for PG I performance, segregation from acids and oxidizers (hydrogen cyanide liberation on contact with acid is the standing nightmare scenario), placarding, and the full marine pollutant documentation and stowage chain. So far, nothing unusual — it’s a well-worn Class 6.1 entry.

Why Sodium Cyanide — And What About the Rest of the Cyanide Family?

It’s a fair question, and worth answering directly rather than leaving it implied: this article centers on sodium cyanide because the Cyanide Code itself does. NaCN is estimated to account for less than a fifth of all manufactured cyanide worldwide — the majority goes into unrelated industrial chemistry — but within that slice, it has been the gold industry’s reagent of choice since 1887, precisely because it’s one of the very few chemicals that will dissolve gold in water. Modern heap-leach and carbon-in-pulp operations run it as a dilute solution, typically 0.01–0.05% cyanide, but the tonnage moving in solid, high-concentration form from producer to mine is what the Cyanide Code’s transport chapter — and the sea-freight audits cited earlier — are built around. It is, in a real sense, the substance the entire certification ecosystem exists to govern; the Code’s own full title specifies “the Production of Gold.”

That doesn’t mean sodium cyanide is the only cyanide compound moving under IMDG Code, or the only one a signatory’s supply chain touches. Potassium cyanide is a genuine second reagent in the same leaching chemistry, and the other entries below sit adjacent to UN 1689 in the same part of the Dangerous Goods List:

For a DG officer, the practical read is this: if your consignment is specifically the gold-leaching reagent, it’s almost certainly UN 1689 or UN 1680, and the Cyanide Code’s Transport Verification Protocol and the packaging language cited earlier apply squarely. If it’s a cyanide-bearing waste stream, effluent, or an unlisted mixture, you’re more likely looking at UN 1935 or a Class 9 environmentally hazardous substance determination instead — worth flagging separately in a future piece, since that’s a classification judgment call rather than a straightforward table lookup.

Where the Cyanide Code Actually Bites Into IMDG Practice

1. The Code’s own text points straight at IMDG

This is the clearest link in the whole picture, and it comes from the Code itself rather than from an audit report. Among the Transport Principle’s Standards of Practice, Transport Standard of Practice 1.5 states plainly: “Follow international standards for transportation of cyanide by sea.” For any signatory moving cyanide by ocean freight, that single clause folds IMDG Code compliance directly into Cyanide Code certification — it isn’t an implication drawn from packaging language elsewhere, it’s the Standard of Practice itself.

It sits alongside two companion Standards worth knowing: 1.1 requires that transport routes be selected to minimize the potential for accidents and releases, and 1.6 requires that shipments be tracked to prevent losses in transit — both of which layer directly onto a carrier’s existing IMDG stowage, segregation, and documentation obligations rather than replacing them.

2. Packaging compliance is written directly into Cyanide Code audits

ICMI’s own certification audit reports cite IMDG Code by name as the packaging standard. A September 2024 transport audit of Taifa Transport & Logistics Ltd’s road leg from the Port of Dar es Salaam to Tanzanian gold mines describes solid sodium cyanide briquettes packed into woven polypropylene bags with PVC liners, inside wooden crates, loaded into 1,000 kg IBCs — with the auditor confirming the packaging “complies with International Maritime Dangerous Goods Code for Group 1 hazardous goods” and has been subjected to the relevant tests required by the Code. Containers in that case load out at a maximum of 20 IBCs, capped at 20 tons of product, sealed and shipped by sea from consignor to the Port of Dar es Salaam.

In other words: passing an ICMI transport audit for an ocean leg already presupposes IMDG compliance. The Cyanide Code doesn’t set an independent packaging standard — it audits against IMDG and treats conformance as a baseline.

3. Ocean carriers can be Cyanide Code signatories in their own right

ICMI’s Transportation Verification Protocol applies to consignors and transporters generally, and that includes maritime carriers. Certified operations have included ocean transport companies audited specifically against the Cyanide Code’s Transport Principles — routing decisions re-evaluated per voyage for weather, political conditions, and other risk factors, shipment tracking, security measures, and emergency response records all sampled during the audit.

For a DG officer at a shipping line moving cyanide on a regular trade lane, that raises a practical question worth flagging to commercial teams: is Cyanide Code certification a competitive differentiator on cyanide-carrying routes, the way P&I club acceptance criteria already function as a de facto qualifying filter?

Who Should Be a Signatory — and Who Gets Audited as a Subcontractor?

This is where a lot of confusion sets in, and ICMI’s own Transportation Guidance is explicit about the structure. Not every entity that touches a cyanide shipment needs to be — or should be expected to be — a Code signatory in its own name. There are two distinct tiers.

Tier 1: Entities that carry direct Code responsibility

Three categories of company can become signatories and bear full responsibility for certification:

• Gold and silver mining companies — certified under the Mining Operations Verification Protocol.
• Cyanide producers — certified under the Production Verification Protocol.
• Consignors — any entity that organizes and oversees a multi-carrier supply chain: producers, distributors, sales agents, brokers, or mining companies. A consignor’s signatory application must list every entity in its supply chain — every trucking company, rail line, shipping company, port, and warehouse — and the consignor carries formal responsibility to ICMI for the compliance of that entire chain.

Trucking companies can also become signatories independently if they choose to seek their own certification rather than being audited as part of someone else’s supply chain.

Tier 2: Entities audited as subcontractors, not separately certified

Within a consignor’s certified supply chain, ICMI applies two different levels of scrutiny depending on what kind of entity is involved:

• Non-signatory trucking companies are evaluated against the full Cyanide Transportation Verification Protocol as part of the supply chain audit — the same questions a standalone signatory would face, just folded into the consignor’s audit report rather than published separately.
• Rail carriers, ports, and ocean/shipping carriers get a lighter-touch Due Diligence Investigation instead of a full Code audit, conducted or reviewed on a three-year cycle. ICMI’s own guidance explains why: full audits aren’t required for these entities “due to security issues, limited access, and the inability of consignors to affect changes in the operating practices of these transport operations.” In plain terms — a consignor can dictate procedures to a contracted trucking firm; it generally cannot dictate operating practice to a global container line.

The practical read for anyone in the supply chain: if you’re a consignor arranging cyanide moves across multiple modes, you carry the compliance obligation for everyone downstream unless they’re independently certified — and you should be prepared to document due diligence on your ocean carriers and ports, not assume the lack of a signatory badge means the Code doesn’t apply. If you’re a trucking company that regularly moves cyanide, independent certification takes you out of someone else’s audit report and gives you your own public compliance record. If you’re an ocean carrier, the Code doesn’t require you to be a signatory at all — but a handful, like IMC, have chosen to be, likely because it removes a due-diligence question mark for every consignor deciding whether to book space with you.

The Interim Storage Question at Ports

This is the most operationally relevant intersection for anyone working port-side. ICMI’s Transport Verification Protocol draws a specific line: a truck parked overnight en route is not “interim storage” and doesn’t trigger the Code’s storage-facility requirements. But a container held at a port or rail terminal awaiting transfer to another mode does count as interim storage — unless the transfer happens within hours rather than over a day or more. For trans-shipment ports and container yards handling cyanide consignments, that means the storage site itself becomes subject to evaluation under the protocol, layered on top of whatever the port’s own IMDG-compliant DG storage segregation already requires.

This is exactly the kind of clause that gets missed by freight forwarders who think of the Cyanide Code as “a mine site thing.” If your terminal handles cyanide transshipment and the dwell time runs past a few hours, you may be inside Cyanide Code scope without realizing it.

Back to the North Sea: What “Empty Uncleaned” Actually Means

Return to the Solong. The distinction the operator drew — laden cargo versus empty uncleaned containers that had “previously contained” sodium cyanide — is not just a PR nuance, and it cuts the opposite way from what a casual reading suggests. Under IMDG 5.1.3.1, a packaging — including an IBC — that previously contained dangerous goods must be identified, marked, labelled, and placarded exactly as required for those dangerous goods, unless steps such as cleaning, purging of vapours, or refilling with a non-dangerous substance have been taken to nullify the hazard. 5.1.3.3 extends the same rule to cargo transport units: an empty CTU still carrying residues, or loaded with empty uncleaned packages, must comply with the provisions applicable to whatever it last contained.

In other words, an empty uncleaned Class 6.1 container isn’t a lesser category with reduced paperwork — under IMDG it is documented, marked, and placarded as if it were still full, right down to the marine pollutant mark, until someone can show it’s been cleaned or purged. That’s a sharper distinction than “not the live hazard early reporting suggested,” and it’s exactly the kind of gap that gets lost between a shipping line’s press statement and a news wire.

Where This Leaves the Practitioner

The takeaway for anyone classifying or moving UN 1689 by sea: IMDG compliance remains the non-negotiable floor. But if your cargo is moving to or from a Cyanide Code signatory — which, given over 320 currently certified operations worldwide, is increasingly likely on any established gold-mining trade lane — expect your transport arrangement, and possibly your port dwell time, to be evaluated against a second, voluntary standard that assumes IMDG compliance and then asks for more.