IMDG Segregation Terms Explained

What the Terms Really Mean

Maybe I am not the only one who was confused by the terms in Section 7 of the IMDG Code. I did some research and wanted to share the results with you. I hope you find it helpful.

Why Segregation Matters

When shipping dangerous goods by ocean, one of the most misunderstood concepts is segregation. The IMDG Code uses simple phrases like “away from” and “separated from,” but those terms carry very specific operational meaning. If misunderstood, they can lead to improper stowage, rejected shipments, or worse — dangerous chemical interactions during transport.

The key is not just knowing the words but understanding how they translate into real-world loading decisions inside a container or on a vessel.

Segregation Code 1: Away From

Let’s start with the most common level: “away from.” This is segregation code 1, the least restrictive. In simple terms, “away from” means the goods can be shipped together, but they cannot be placed directly beside each other. A shipper can load these materials in the same container, the same hold, or on the same deck, as long as there is some physical distance between them. That distance is often achieved by placing the materials on separate pallets, using dunnage, or positioning them at opposite ends of the container. The easiest way to explain this in training is: “You can ship them together — just don’t let them touch.”

Segregation Code 2: Separated From

The next level is “separated from,” or segregation code 2. This is where things become more restrictive. “Separated from” means the goods cannot simply be spaced apart — they must be divided by a structural barrier or placed in different compartments. In practice, this often means separate containers or different holds on a vessel. While the IMDG Code allows for equivalent separation methods, most real-world shippers will not attempt to engineer barriers inside a container. Instead, they make the practical decision to split the shipment. A simple way to explain this is: “these can’t share the same space — you need a wall between them.”

Segregation Code 3: Separated by a Complete Compartment or Hold From

Moving up, we have “separated by a complete compartment or hold from,” which is segregation code 3. This requirement is specific to vessel stowage and goes beyond what a shipper can control during packing. It means the two types of dangerous goods must be placed in entirely different enclosed spaces on the ship, separated by a full compartment or cargo hold. Even if both are below deck, they cannot be in the same hold under any circumstances. From a training perspective, this can be simplified to: “not just a wall — they must be in completely different rooms of the ship.”

Segregation Code 4: Separated Longitudinally by an Intervening Complete Compartment or Hold From

Finally, the most restrictive level is “separated longitudinally by an intervening complete compartment or hold from,” or segregation code 4. This adds an additional layer by requiring separation not only by a full compartment, but also along the length of the vessel. In other words, the dangerous goods must be placed in different holds with at least one full hold in between them. This ensures maximum distance and isolation in case of fire or reaction. The simplest way to explain this is: “they must be far apart, with an entire space between them.”

The Impact of Subsidiary Hazards

What makes segregation particularly important is that it is driven not just by primary hazard classes, but also by subsidiary hazards. A product that appears compatible at first glance may trigger stricter segregation due to an additional hazard, such as an oxidizing or toxic subsidiary class. This is why classification is so critical — it directly determines how a shipment can be built.

Applying Segregation Rules in Real-World Shipping

In real-world shipping, most decisions come down to a simple question: can everything go into one container safely and compliantly? If the segregation requirement is “away from,” the answer is usually yes, provided distance and careful loading are used. If it is “separated from” or higher, the answer is often no, and the shipment must be split. Understanding these distinctions allows shippers to make faster, safer, and more compliant decisions.

Final Thoughts

At its core, IMDG segregation follows a simple progression: first, you separate by space, then by structure, and finally by distance across the vessel. When explained clearly, these rules are not just regulatory requirements — they are practical tools to prevent dangerous interactions at sea.

Confused about IMDG segregation requirements? ICC Compliance Center can help! Strengthen your knowledge with our IMDG training courses or contact our team to learn how we can support your dangerous goods shipping needs.