Segregation techniques
Segregation using distance or inert materials
Segregation by use of cut-off storage
Segregation by using detached storage
When it comes to segregating dangerous goods the following methods are generally used:
- segregation by distance or by the use of inert materials
- segregation by the use of cut-off/partitioned storage areas
- segregation by the use of detached storage
- ensuring that incompatible goods are not stored above one another.
Segregation using distance or inert materials
The use of distance or inert (mutually compatible) materials between incompatible goods can be used when materials will not react violently together. A minimum separation distance of 3m will generally be suitable for most dangerous goods of packing group III.
Extra care should be taken with dangerous goods assigned to packing group II, as these can be more reactive or more dangerous in other ways (e.g. highly toxic). Where one or more of the incompatible goods are assigned to Packing Group II, or if they may react dangerously (e.g. calcium hypochlorite and petrol), a minimum segregation distance of 5m is recommended.
Where a violent reaction between dangerous goods may occur it may be necessary to consider storing such goods in separate compartments or rooms (cut-off storage). The HAZCHEM Code can be used as a tool to indicate whether there is an increased likelihood of a violent reaction. If the second digit in the HAZCHEM Code is a P, S, W or Y, the possibility of a violent reaction should be considered for that dangerous goods.
In the case of incompatible liquids, curbing, ramps, bunding or depressed floor areas can be used to prevent the flow and interaction of incompatible liquids. Distances should be measured from the edge of the spills catchment system.
Where both incompatible goods are solids and such solids are not likely to melt in the event of a fire, the minimum segregation distance can be reduced to 1m apart.
Segregation by the use of distance or inert materials may be suitable for dangerous goods such as class 3 dangerous goods and class 6.1 goods or ordinary combustible matter (not combustible liquids) and oxidising agents.
'React dangerously' means to react in a manner that directly creates a hazard due to the reaction:
- being violent
- producing an explosion
- producing a potentially explosive combination of products
- producing a fire or rapid evolution of heat
- producing toxic vapour or toxic gas.
Segregation by use of cut-off storage
The use of separate rooms or enclosures to isolate incompatible goods is known as 'cut-off' storage. Segregation involves storing incompatible goods in separate compartments or rooms within a building. The rooms are separated by a fire rated partitions that are impervious to vapours and liquids. A fire resistance wall of at least FRL 120/120/120 fire rating for the partition is recommended.
Use of partitioned areas is useful for those materials that may react violently or offer high burning rate (e.g. large stores of class 4.2 or 5.2 dangerous goods).
Segregation by using detached storage
Detached storage segregation involves storing incompatible dangerous goods in separate buildings. This kind of segregation is used for materials that possess severe fire, reactivity or health risk.
'Dangerous when wet' goods such as aluminium phosphide and calcium carbide are materials that would warrant such precautions. Aluminium phosphide reacts with water to give off phosphine, a toxic and flammable gas. Calcium carbide reacts with water to generate acetylene gas. A separate building without water fire protection systems is needed to ensure water is not applied to these materials.
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