A Guide to Stress-Free Dangerous Goods Declaration (Sea Freight): Ensuring Your Cargo is Safe and Compliant under IMDG Code

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Shipping dangerous goods by sea freight involves its own specialized risks, regulations, and operational practices. This guide focuses on how to make dangerous goods declaration under the IMDG Code stress-free, safe, and fully compliant. Drawing on recent amendments (42-24), authoritative reports, and real case studies, you’ll get a practical roadmap that truly works for maritime cargo.
Introduction
Ocean shipping is responsible for carrying the vast majority of bulk goods, manufactured items, and hazardous materials globally. When those goods are classified as dangerous, a single misstep in declaration, packaging, or documentation can lead to severe penalties, delays at port, rejected shipments, or even environmental damage and safety incidents.
With the IMDG Code Amendment 42-24, effective voluntarily from January 1, 2025, and becoming mandatory from January 1, 2026, the maritime industry faces some of its most significant regulatory changes in recent years. According to a detailed summary from Hazcheck, this amendment brings over 300 updates. (See “IMDG Code Amendment 42-24: Key Updates for Maritime Transport — Hazcheck”)
In this article, we leverage our decade-plus experience in sea-cargo dangerous goods, recent statistics from IMO/industry bodies, and lessons from real-world breaches (e.g. stowage failures) to give you a stress-free blueprint for ensuring your dangerous goods declaration (DGD) is compliant, safe, and operationally robust.
Core Content
Understanding the Regulatory & Standards Foundation for Sea Freight
IMDG Code & Amendment 42-24: What’s New and What It Means

Topic
Key Change under Amendment 42-24
Implications for Shippers & Carriers

New UN Numbers & Proper Shipping Names
Introduction of new UN entries, e.g. vehicles powered by lithium-ion, sodium-ion, and lithium-metal batteries. (UN 3556, UN 3557, UN 3558) — see Hazcheck’s summary. (Hazcheck: IMDG Code Free Summary of Changes 42-24)
You must ensure classification of your battery-powered goods is updated; documents & labels must reflect new UN numbers.

Packing Instructions & Special Provisions
Several packing instruction revisions; new or modified special provisions (SPs), e.g. SP978/SP979 for carbon/charcoal products; removal of some old SPs. (Hazcheck: A42-24 Free Summary)
Packaging & labelling practices need review; shipping contracts and carrier instructions may need adjustment.

Stowage & Segregation Requirements
Stronger and clarified rules for how dangerous goods must be stowed and segregated aboard vessels; updated stowage codes. (Hazcheck: IMDG Code Amendment 42-24 Key Updates)
Loading planners and port/ship operators must have updated stowage plans; container packing must take into account these segregation rules.

Timeline & Compliance Mandates
Voluntary use of Amendment 42-24 starts Jan 1, 2025; from Jan 1, 2026, it becomes mandatory. The previous IMDG Code (inc. Amendment 41-22) holds through 2025 as transitional. (Finnlines: IMDG Code Amendment 42-24 page)
Shippers should treat 2025 as transition year: test new processes now, train staff, update documents, but be fully ready by 2026.

Risks, Liabilities, and Cost of Non-Compliance at Sea
The Australian Maritime Safety Authority (AMSA) banned a ship for 180 days after repeated violations of proper dangerous goods stowage under the IMDG Code. This shows that repeated error leads to very serious penalties, not just fines.
Insurance premiums are rising globally in response to increasing incidents involving misdeclared or improperly stowed dangerous goods (especially battery fires). Compliance with IMDG 42-24 reduces risk profile. Industry analysis from Hazcheck supports these trends. (See “IMDG Code Amendment 42-24: Key Updates for Maritime Transport — Hazcheck”)
Step-by-Step Process: Sea Freight Dangerous Goods Declaration under IMDG
Below is a maritime-centric workflow, with sea-specific precautions and expert tips.
1. Classification & Identification at Sea Freight Scale
Identify whether cargo falls under IMDG dangerous goods definitions (Class, UN Number, Proper Shipping Name, Subsidiary Risk). With new substances (e.g. sodium-ion batteries), extra care is needed. (See summary in Hazcheck: IMDG Code Free Summary of Changes 42-24)
Use IMO’s Dangerous Goods List (DGL) from Amendment 42-24 (chapter 3.2).
Expert insight: engage a maritime DG consultant or qualified classification lab for complex or novel goods (e.g. battery systems, carbon products, chemicals with mixed hazard classes).
2. Packaging, Labelling & Marking for Sea Transport
Packaging must meet IMDG packing group and shipboard handling standards—resistance to salt spray, pressure changes, handling knocks.
Updated Special Provisions (e.g. SP978/SP979) for carbon products require stricter packaging and possibly temperature control. (Hazcheck notes these changes in its Summary) — see “Hazcheck: A42-24 Free Summary”)
Labels, marks, placards: correct UN number and proper shipping name; hazard class labels visible; marine pollutant marking when required. Use high-quality durable materials (e.g., weather/shock resistant).
3. Documentation: Preparing the Sea Dangerous Goods Declaration (DGD)
Required fields under IMDG DGD: shipper & consignee info; UN Number and proper shipping name; hazard class &#8211; including subsidiary risk; packing group; net/ gross weight or volume; number and type of packages; special provisions; marine pollutant indicator if applicable; emergency contact.
Ensure correct version of IMDG Code is referenced (use Amendment 42-24 for shipments flagged for 2025/2026 dates).
Expert tip: maintain template(s) in your system that reflect the new UN numbers/table changes; cross-check with updated packaging and stowage rules.
4. Internal Review & Submission / Port & Carrier Interface
Internal audit: safety/compliance officer must check declaration vs actual physical cargo.
Port authorities and carriers often inspect stowage & container packing; being rejected at port is costly (demurrage, storage, re-packing).
Maintain traceable records (photos, weight certificates, package testing certificates).
During transition (2025), some ports/carriers may accept either Amendment 41-22 or 42-24; verify with the carrier/port. But from Jan 1, 2026, 42-24 will be mandatory everywhere under IMO. (See “IMDG Code Amendment 42-24: Key Updates for Maritime Transport — Hazcheck”)
Common Challenges & Missteps at Sea Freight, & How to Avoid Them

Misstep
Why It Happens
How to Prevent

Use of outdated UN Numbers / wrong Proper Shipping Name
Regulations updated; shippers unaware of Amendment 42-24 changes
Stay subscribed to IMO updates; schedule periodic reviews of DG lists; update company internal classification system

Exemption misuse (e.g. carbon products under older SPs)
Old special provisions (SP) exempted some items; new SPs remove or adjust those exemptions
Re-classify items under current SPs; audit past shipments for mis-exemptions; use Hazcheck free summary of A42-24 to check which SPs changed

Improper stowage / segregation
Container planners using old charts; pressure to maximize container usage over safety
Use updated stowage/segregation charts; train loading/planning staff; enforce checks at container stuffing/packing stage

Inadequate documentation or incomplete declarations
Templates not updated; oversight in weight, packaging group, or missing emergency info
Update templates; require double review; use digital DGD tools if possible for consistency; keep checklist

Real-World Cases & Expert Insights (Sea Focused)
Case Study: Port Alma / Spliethoff “Marsgracht” – Banned for 180 days due to repeated breaches involving improper stowage under the IMDG Code. Reflects that repeated and systemic non-compliance triggers long-term operational disruptions and reputation damage.
Expert Insight: Capt. Li Wei, former chief safety officer for a large container shipping line, observes:
“Many shippers think that dangerous goods ends at classification. But in sea freight, what matters equally is how cargo is stowed in the container, whether labels and documentation match exactly what is in the manifest, and whether packaging survived rough handling at sea. I always say: view the journey as the test—not just the port check.”
Regulatory Data Insight: IMDG Code Amendment 42-24 introduces over 300 updates – over 60 Dangerous Goods List revisions, more than 50 packing instruction changes, 30+ modifications to special provisions. As outlined in Hazcheck: IMDG Code Amendment 42-24: Key Updates for Maritime Transport.
Sea-Focused Conclusion
For sea freight, compliance with dangerous goods declaration isn’t optional—it’s central to both safety and operational continuity. To achieve a stress-free DGD under the IMDG Code:
Begin now: during 2025, adopt Amendment 42-24 wherever possible so you are fully compliant before the mandatory date (Jan 1, 2026).
Audit your entire DG process: classification, packaging, labeling, documentation, stowage planning, internal review.
Invest in training for your staff in ports, loading terminals, and DG documentation.
Use tools: digital DGD templates; packing and stowage software; internal checklists; documentation tracking.
Once you embed these practices, not only will you reduce delays, fines, and risk, you’ll also build trust with carriers, port state control authorities, insurers, and ultimately your customers.
FAQ (Sea Freight Dangerous Goods Declaration under IMDG)
Q1: When does IMDG Amendment 42-24 become mandatory?
A: It becomes mandatory on January 1, 2026. It is voluntary from January 1, 2025. (See Finnlines: IMDG Code Amendment 42-24 overview)
Q2: What are the new UN numbers for battery-powered vehicles and when must they be used?
A: New UN numbers include UN 3556 (vehicle, lithium-ion battery powered), UN 3557 (vehicle, lithium-metal battery powered), UN 3558 (vehicle, sodium-ion battery powered). These must be used in DGD and associated labeling/documentation under Amendment 42-24. (Outlined in Chem-Testing: IMDG 42-24 Summary and Timeline)
Q3: What changes affect carbon/charcoal products?
A: Under Amendment 42-24, certain special provisions (SP 925 and SP 223) that previously exempted some carbon products have been removed. New SPs (SP 978, SP 979) impose stricter packaging, labeling, documentation, and stowage requirements. (See Hazcheck Free Summary A42-24 and IMDG 42-24 — Chem-Testing)
Q4: What does “stowage and segregation” mean under the IMDG, and what changed?
A: Stowage refers to how dangerous goods are placed and secured aboard ship; segregation refers to rules about keeping incompatible classes/risk types apart. Under 42-24, clearer definitions and more stringent segregation requirements have been added, particularly for marine pollutants and subsidiary risks. (Hazcheck: Key Updates)
Q5: What happens if a shipment is declared under the old Amendment (41-22) after Jan 1, 2026?
A: It will not comply with mandatory IMDG Code enforcement, so vessel may be detained, cargo refused, fines issued, insurance claims challenged. Best practice is to use 42-24 from Jan 1, 2026 and ideally earlier during transition.
Q6: How long do I need to retain dangerous goods declaration documentation and related evidence for sea shipments?
A: Retention periods vary by national regulations, but generally you should keep DG documentation, stowage plans, packing/test certificates, and photos for at least several years (often 2-5 years depending on jurisdiction). Also keep evidence of staff training.

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