Shipping Chemicals Internationally: SDS, DG Class, Packaging, and Booking

"Chemicals" is a broad category that covers everything from an inert industrial cleaning agent to a highly reactive solvent, and the shipping requirements for each differ enormously. What ties them together is that none of them can be booked the way a routine general-cargo shipment is booked — every chemical has to go through a classification step first, and depending on what that step finds, the shipment may or may not turn out to be dangerous goods at all. This article walks through what that classification step involves, how it flows into packaging and documentation, and what a forwarder and carrier each check before accepting a chemical shipment for booking.

What the Safety Data Sheet (SDS) Establishes First

The SDS is the document that starts everything. It's prepared by the manufacturer or supplier of the chemical, typically following a standard 16-section format that covers composition, physical and chemical properties, hazard identification, first-aid measures, and — critically for shipping — a transport information section. That transport section is where the manufacturer states the substance's proper shipping name, UN number, and hazard class as they understand them, based on the substance's known properties.

A forwarder or carrier's classification work starts from this document, not from the product's commercial name or marketing description. Two products with similar-sounding names can carry very different hazard profiles depending on their actual composition and concentration, which is exactly why the SDS — not the label on the outside of the box — is the reference point. If an SDS is missing, out of date, or doesn't match the actual substance being shipped, nothing downstream — packaging, declaration, or booking — can proceed reliably, because everything else in the process is built on what the SDS says.

Determining DG Class and Packing Group

Once the SDS confirms a substance is dangerous goods, it's assigned to one of nine internationally recognized hazard classes — covering categories such as flammable liquids, flammable solids, oxidizing substances, toxic substances, corrosives, and a miscellaneous category for hazards that don't fit the others cleanly, among the full set of nine. Which class a substance falls into depends on its actual physical and chemical hazard properties as documented in the SDS, not on how dangerous it sounds or looks.

Within most of these classes, substances are further assigned a packing group — I, II, or III — reflecting the degree of danger the substance presents, from greatest (I) to least (III). Packing group matters practically because it drives the packaging performance standard required: a packing group I substance needs packaging tested and certified to a more demanding standard than a packing group III substance in the same class. Getting class and packing group right isn't a formality — it's the input that everything downstream, from which drums or IBCs are acceptable to how the shipment must be labeled, is built on.

For ocean shipments specifically, the SDS's environmental hazard section feeds one more determination: whether the substance qualifies as a marine pollutant under the IMDG Code. This designation is separate from the hazard class and packing group — a substance can carry a marine pollutant designation on top of its class 3, 6, or 8 hazard rating, for example, and even some substances that aren't dangerous goods at all in every other respect can still trigger marine pollutant marking if their SDS environmental data crosses the relevant threshold. Missing this designation is a common gap in chemical shipments prepared by someone used to air or road dangerous goods rules but less familiar with the IMDG Code's ocean-specific requirements.

Packaging to UN Specification

Once class and packing group are confirmed, packaging has to match a UN specification rated for that combination — not simply be strong enough to the eye. UN-specified packaging, whether a steel or plastic drum, an intermediate bulk container (IBC), or a combination package with an inner and outer layer, carries a UN mark on the packaging itself showing the packaging type, the packing group it's rated for, and other identifying data confirming it was tested to the relevant performance standard — drop tests, stacking tests, and leakproofness tests among them, depending on the packaging type.

Using packaging that isn't UN-rated for the substance's actual class and packing group is one of the most common — and most consequential — errors in chemical shipping, because it isn't caught by a visual check alone. A drum that looks perfectly adequate can still be the wrong rating for what's inside it, which is exactly the kind of mismatch a forwarder experienced in dangerous goods is checking for before a booking is confirmed, not after the cargo has already been packed and sealed.

Preparing the Dangerous Goods Declaration

The dangerous goods declaration is the shipper's formal statement to the carrier of exactly what's being shipped: the proper shipping name, UN number, class, packing group, quantity, and the type of packaging used, along with a declaration that the shipment has been prepared in accordance with applicable requirements. It's typically signed by someone trained and authorized to certify dangerous goods shipments, whether that's staff at the shipping company or a forwarder acting on the shipper's behalf.

The declaration has to match the SDS exactly. If the SDS says one hazard class and the declaration states another, or if the packing group on the declaration doesn't correspond to the packaging actually used, that mismatch is exactly what a carrier's dangerous goods acceptance check is designed to catch — and it's one of the most common reasons a chemical booking gets held up rather than accepted on the first attempt. Building in time to review the declaration against the SDS before submission is generally worth far more than the few minutes it takes.

Booking with a Forwarder Experienced in Dangerous Goods

Not every carrier accepts every class of chemical, and not every mode accepts every class either — some substances that ship without issue by sea are restricted or forbidden on passenger or cargo aircraft specifically, because of the different risk profile of an incident occurring in the air versus at sea. A forwarder experienced in dangerous goods generally knows which carriers on a given route accept which classes before a booking attempt is made, rather than finding out after a booking request has already been submitted and rejected.

Segregation is a related, separate consideration. Certain classes of dangerous goods can't be stowed near certain other classes — an oxidizer and a flammable substance, for example — which affects whether a chemical shipment can be consolidated into a shared container or air pallet with other cargo, or whether it needs to move on its own. This is worth raising with a forwarder early, particularly for LCL or air consolidation, since segregation requirements can rule out sharing space that would otherwise make sense on cost grounds.

Common Points Where Chemical Shipments Get Held Up

A handful of recurring issues account for most of the delays chemical shippers run into: a dangerous goods declaration that doesn't match the SDS in class, packing group, or quantity; packaging that isn't UN-rated for the actual substance shipped, discovered only at the point of carrier acceptance; a mismatch between what's stated on the label of the outer packaging and what's declared on the paperwork; and booking a mode or route without first confirming the carrier accepts that specific class of chemical, resulting in a rejected or delayed booking.

None of these issues is unusual or exotic — they're the predictable result of skipping the classification-first sequence and trying to fit chemical cargo into a general-cargo booking process. Building the classification, packaging, and declaration work into the timeline from the start, rather than treating it as paperwork to finish just before the cargo ships, is what keeps a chemical shipment moving on schedule.