Substances that are chemically unstable such as self-reactive substances, organic peroxides and substances liable to polymerize shall not be accepted for transport unless stabilization precautions have been taken to prevent the possibility of a dangerous exothermic decomposition or polymerization.

Stabilization may require temperature control or addition of stabilizing chemicals, or a combination of both. Control and emergency temperatures must be specified on the shipper’s booking information and in the transport document for temperature controlled transport. Additionally, the word “STABILIZED” must be included on the transport document.

Note: for substances which have the word ‘Stabilized’ added as part of the proper shipping name in accordance with 3.1.2.6, stowage category D and SW1 (protected from sources of heat) will apply.

If stabilization is by temperature control the words “TEMPERATURE CONTROL” must also be added to the proper shipping name as per 3.1.2.6.2.

Carriage of temperature controlled dangerous goods is likely to be subject to monitoring at sea, so deck stowage is usually required that allows temperature checks and direct access for emergency response.

Polymerizing substances may be found in Class 2 (Gases), Class 3 (Flammable liquids), Class 6.1 (Toxic) and Class 8 (Corrosive). Polymerizing substances that do not meet the criteria for other hazard classes are allocated Class 4.1. These are subject to special carriage conditions⁹⁹.

Control temperature

Control temperature is the maximum safe temperature at which self-reactive or polymerizing dangerous goods that are sensitive to temperature should normally be carried. It is set at a margin below the Self-Accelerating Decomposition Temperature (SADT), and if this temperature is exceeded, intervention and possible cargo jettison will be considered.

Emergency temperature

The temperature at which substances required to be carried at a controlled temperature become unstable, will spoil or begin to react dangerously and should trigger alarm systems.

-

⁹⁹ IMDG Code, 2022 Edition Amendment 41-22, Sections Special Provision 386 and 7.3.7