2.7 The Concept of Compatibility Relating to Dangerous Goods

Compatibility tools are only intended for use in workplaces where dangerous goods are stored. It is not intended for transport situations where the ADG Code should apply. It is not intended for application against open (in use) packages kept on a shelf or bench top within a laboratory, workshop or similar situation. Radioactive materials (class 7) and explosives (class 1) should be deemed incompatible with all other dangerous goods.

How to use the tool

• Identify if the material is a dangerous good or combustible liquid (a combustible liquid has a flashpoint above 61 degrees Celsius) using the MSDS/label.
• Identify the class, subsidiary risk and packing group (where relevant) of each of the two dangerous goods you intend to store together.
• Where goods are also combustible liquids this should be regarded as a 'subsidiary risk' for consideration.
• Use the chart below to ensure that the goods and/or combustible liquids are compatible by aligning where the vertical and horizontal axis meet.
• Check and repeat this process for any subsidiary risks that either of the goods may have.
• It is recommended that an MSDS be consulted to ensure the materials are compatible. Goods with different UN numbers within the same class may be incompatible.
• Follow the directions provided using the compatibility chart key, checking all guidance notes and supplementary notes.
• Where goods are incompatible consider greater separation if the packing group is PG I or II irrespective of the symbol used to account for the higher level of danger.

Compatible goods

Two or more goods are compatible provided their interaction does not give rise to any of the following outcomes:

• Harm to persons, property or the environment.
• Fire, or explosion, generation of toxic, flammable or corrosive vapours/gases.
• Accelerate the combustion of other goods/liquids in the event of a fire.
• Release of the contents results in the premature degradation/corrosion of other dangerous goods or combustible liquids' packaging/means of containment.
• During the event of a fire/spill/release, the interaction of dangerous goods/combustible liquids with incompatible firefighting or dispersal media. Some materials are water-reactive and should be stored away from other goods that are reliant on water or foam as a fire fighting/dispersal/suppression media).

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Compatible goods guidance notes

• In most cases, materials of the same class will be compatible. However, not all materials with different UN Numbers will always be compatible. The MSDS should be checked.
• In many cases, the goods will be compatible. Must check for subsidiary risk compatibility. Please check the MSDS.
• If one of the goods present is also a 'fire risk substance' (one of class 2.1, 3, 4, 5, a combustible liquid or has a subsidiary risk of one of these) or elevated temperature goods, segregation is required by at least 3 m or more. Sub-risk MUST be considered. Other exceptions apply. Please check the MSDS.
• Not all class 5.1 goods are compatible as follows:
  • Ammonium nitrate is not compatible with tetranitromethane, dichloroisocyanuric acid, any bromate, chlorate, chlorite, hypochlorites, chloroisocyanurate, or any inorganic nitrate; and
  • Calcium hypochlorite (and its mixtures) are incompatible with dichloroisocyanuric acid, ammonium nitrate, or any chloroisocyanurate.
  • Organic peroxides are highly reactive materials. Please check the MSDS to ensure compatibility.
  • Where one of the goods to be stored together is a concentrated strong acid and the other a concentrated strong alkali, they should be deemed incompatible.
  • Class 4.3 goods must not be stored next to goods that are in a solution containing water, or where water or foam is the chosen fire fighting/spill/leak dispersal or suppression media for the storage area.
  • Except where class 6.1 is cyanide and class 8 is an acid. Please check the MSDS.
  • Toxic gases ammonia and chlorine must be segregated due to the risk of explosion. It is important to refer to the MSDS for incompatibilities within this class division. It is strongly recommended that each different toxic gas (Class 2.3) be segregated unless the information in the MSDS says otherwise.

Supplementary notes for use with segregation tool

1. Class 2 dangerous goods are generally not recommended to be stored with any other class of dangerous goods particularly flammable dangerous goods due to the risk of flame impingement. Corrosive goods can cause damage to the gas cylinder walls and thus should be kept away from class 2. In a fire, gas cylinders need to have copious quantities of water applied to keep them cool. Toxic gases are stored away from other gases to minimise the release of toxic gases in a fire with other gases.
2. Class 6.1 dangerous goods are not recommended to be stored with fire-risk goods or gas cylinders. In the event of a fire, the toxic material will be liberated and may be spread more effectively due to the heat of the fire or the explosion of gas cylinders.
3. Two or more goods within the same class with incompatible subsidiary risk should be kept apart.
4. The packing group (PG) of dangerous goods denotes the magnitude of danger the material poses from its hazard. PGI is the most dangerous. PG II these are more dangerous than PG III. If one of the incompatible materials is a PGI or II dangerous good, it is recommended that a greater segregation distance or other means of segregation is employed.
5. If class 4.3 dangerous goods are stored or handled care needs to be taken to segregate these away from all containers of aqueous (water-containing) solutions even if the solutions are not dangerous goods. The areas these materials are stored in must not be serviced by a water-based fire suppression system.
6. If one of the incompatible goods is a liquid OR a solid that is likely to melt from the heat of a fire, separate spill catchment systems or means of separating the incompatible goods must be considered. Solid dangerous goods should not be stored in direct contact with the floor surface to avoid contact with liquids.
7. Fire-rated walls constructed of appropriate impervious, chemically resistant materials may be used if provided with an FRL of 240/240/240. Timber structures are not appropriate barriers.
8. In the case of incompatible gases in cylinders intended for use in welding (such as acetylene and oxygen), these gases may be stored together in a purpose-built cradle and separated when not in use for extended periods of time.
9. For oxidizing agents: although only dangerous goods and combustible liquids feature in the compatibility chart care must also be taken to segregate oxidizers from those dangerous goods and other materials that are combustible in nature (e.g. polymeric beads, cotton bales, excess packing materials). Chlorine and some other halogens are considered potent oxidizers even though their class and assigned with any oxidizing agent subsidiary risk under the dangerous goods classification system.