The IMDG Code details specific stowage and segregation requirements by the use of codes and references in columns 16a and 16b of the Dangerous Goods List.

There are also more general segregation requirements based on hazard classes in a segregation table that can be found in Part 7, Chapter 2. Before we look at stowage, handling and segregation in more detail, it is important to understand that the ship's design will restrict where certain classes of dangerous goods can be stowed.

This is due to the hazards presented and the availability of systems to deal with any emergency. Ships that have cargo spaces intended for the carriage of dangerous goods must carry a document of compliance, which certifies that the ship meets SOLAS requirements for these cargoes.

The annex or schedule to this document specifies the restrictions for their stowage within the cargo area. This usually comes in the form of a matrix that allows the cargo officer to determine which hazard class can be stowed where.

Dangerous goods classifications are entered in the rows of the table.

Numbers representing cargo spaces are entered in the columns.

The number of the cargo space is indicated in a simple diagram of the ship and refers to a cargo hold or deck cargo stowage area. The table shown is typical and is populated with either the letter P for permitted or X for not permitted. Alternatively, the words yes and no may be used. Now that we understand the matrix in principle, let's try an exercise. Is it permitted to place a cargo with the following hazard class in hold number 7? How did you get on? The correct answer is no. The hazard label indicates that the cargo contains dangerous goods with hazard class 4.2. By entering the matrix, we see that these are not permitted in hold number 7 or 8, but would be acceptable in any other cargo space. We've just considered stowage based upon the limitations imposed by the ship. Now let's look at the stowage requirements based on the dangerous goods list. If there are any particular stowage requirements, these will be shown in column 16a of the dangerous goods list, which will contain alphanumeric codes that can be used to reference any particular stowage requirement.

There are three different codes that could be displayed. It may be a stowage category code. These codes specify whether goods can be stowed on deck or under deck, under what conditions and the particular requirements if passengers are carried.

The codes are either letters A to E for all hazard classes except hazard class 1, or numbers 1 to 5 for explosives. It may be a stowage code consisting of SW followed by 1 or 2 numbers.

These codes refer to descriptions of very specific stowage requirements. They may include ventilation requirements or additional safety precautions.

It may also be a handling code, consisting of H followed by a single digit. This code refers to the conditions under which the consignment of dangerous goods is transported.

Now that we know what codes we may find, let's try an exercise. Use the dangerous goods list to determine the stowage category, stowage codes and handling codes of UN1386 Seed Cake.

Click the arrow when you are ready to proceed. What information did you find? If you got stowage category E, stowage codes SW1 and SW25 and handling code H1, congratulations!

You got the right answer. You can now use the dangerous goods list. If you got a different answer, try the exercise again to make sure you understand how to use the dangerous goods list.

We've just looked at the document of compliance and column 16a of the dangerous goods list, which identifies where and under what conditions dangerous goods can be stowed.

Now let's consider column 16b of the dangerous goods list. This may display 1 or 2 alphanumeric codes that refer to specific segregation requirements based on a particular substance.

A segregation group consisting of SGG followed by 1 or 2 numbers classifies substances into groups having similar chemical properties. A segregation code consisting of SG followed by 1 or 2 numbers refers to the segregation requirement from other segregation groups.

You can find more information in part 7, chapter 2.

Now that we know what we're looking for, let's try an exercise. Use the dangerous goods list to determine the segregation group and segregation codes for UN1824, sodium hydroxide solution. Click the arrow when you are ready to proceed.

Did you get SGG18 and SG35? If you did, well done. If you got something different, try the exercise again.

Now that we have the segregation code for UN1824, sodium hydroxide solution, let's see how we can use it to determine segregation requirements.

In part 7, chapter 2 of the IMDG code, the segregation group table describes SGG18 as alkalize. This means sodium hydroxide is included in a group called alkalize.

The segregation codes table describes code SG35 as stow separated from the segregation group acids. If we look at the table of other stowage codes, we notice other terms used to identify the levels of separation. Each term starts with the words away from or separated from. The IMDG code identifies four segregation requirements. These are away from, separated from, separated by a complete compartment or hold from, and separated longitudinally by an intervening complete compartment or hold from. The actual definition of these terms depends on the ship type.

These are specified in part 7 of the IMDG code. Chapter 4 deals with container ships, chapter 5 deals with row row vessels, and chapter 6 deals with general cargo ships.

We will look at each of these in more detail a little later in the module.

Before we look at how the level of segregation is specified for different ship types, let's take a few minutes to understand how we can determine the actual segregation requirement between incompatible classes of dangerous goods. The level of segregation between two dangerous goods of different hazard classes or divisions can be determined using the segregation table shown in part 7, chapter 2. The rows and columns are labelled with different hazard class or division. You can determine the segregation degree by entering the table with the different hazard class or division. Where X appears, you must consult the relevant section of the IMDG code. However, the segregation requirement must take any subsidiary hazard into consideration. The highest level of segregation must always be used. For example, if you want to know the level of segregation between substances from hazard class 4.2 and 5.2, entering the segregation table tells you that segregation 2 separated from is required.

Now that you've seen how to determine the different level of segregation, let's take a look at how you interpret these for different ship types, starting with container ships.

Part 7, chapter 4 of the IMDG code provides tables for the user to determine the horizontal and vertical segregation requirements for container ships fitted with hatches and those that are not. The segregation requirements 1, 2 and 3 are defined for closed and open containers for vertical separation and horizontal segregation. Vertical separation states whether containers are permitted on top of one another or in the same vertical line. Horizontal segregation states the container spaces required. In some cases this may include bulkhead separation requirements. The requirements for segregation level 4 are a little different. Vertical segregation and horizontal or thwart ship segregation is not permitted. Horizontal fore and aft segregation is based on a minimum distance of 24 metres and possibly a minimum number of bulkheads. Illustrations regarding the segregation requirements are shown in IMO

Marine Safety Committee Circular 1440, which can be found in the supplement to the IMDG code. Here is a simplified version of open versus closed containers on a container ship fitted with hatches. Part 7, chapter 5 provides a table for the user to determine the horizontal segregation of cargo transport units on row-row vessels. As with container ships, there is a table specifying the segregation requirements based on the four segregation groups defined earlier. The table identifies the segregation requirements for a thwart ships and fore and aft for both closed and open cargo transport units. The segregation requirements are specified in terms of distance, bulkheads and whether on deck or under deck. Again, illustrations regarding the segregation requirements are shown in IMO Marine Safety Committee Circular 1440, in the supplement to the IMDG code. Part 7, chapter 6 of the IMDG code applies to segregation of packaged dangerous goods stowed in the conventional way. This includes particular segregation from foodstuffs. The different segregation requirements are specified in terms of horizontal distance and vertical separation from packages containing incompatible dangerous goods. This takes into account any fire and liquid resistant compartments when considering vertical segregation. Where dangerous goods in packages are stowed together with a cargo transport unit containing dangerous goods, no segregation between the packages and the cargo transport is needed when away from is required. Where separated from is required, the segregation for away from is sufficient. Where segregation between packaged dangerous goods and those carried in bulk under the IMBSC code, the segregation requirements are specified in a table similar to the segregation table specified earlier. The definitions of the four segregation terms are also defined for such a stowage arrangement in a similar way as described earlier in this section. Before we move on to the next chapter, let's consider some questions. The following two closed cargo transport units are to be stowed on a row-row cargo area on the deck. CTU-A, UN-1469, lead nitrate PG-2. CTU-B, UN-3291, clinical waste PG-2. Using the IMDG code, which one of the following is the minimum horizontal level of segregation that meets the IMDG code? The following consignment is to be stowed as general cargo on a supply boat. UN-3374, acetylene, solvent free. Which of the following are specific stowage requirements for this consignment? The following cargo needs to be carried on deck with a general cargo ship with conventional stowage arrangements.

UN-1203, gasoline, portable tank container. UN-1362, activated carbon, packages. Which of the following is a suitable minimum segregation requirement?

Dangerous goods closed container, MSKU-3894911, is shown in red. Drag the blue closed container,

MSKU-3894758, to the required a thwart ship stowage position.