IMDG Code specifies various conditions of the carriage of dangerous goods in packaged form. Shippers need to make sure that all these conditions are followed when shipping the dangerous goods.
For example, the dangerous goods need to be segregated as per the IMDG code to avoid two incompatible goods to come in contact with each other.
IMDG Code deals with DG in packaged form. It has all the information on how a dangerous good need to packed and how much quantity can be in a single packing.
Let us say that for a packing group required for a DG, the maximum allowed quantity in one pack is 200KG.
One shipper transports 200 KGs of this DG in one packing and other shipper makes 40 packages each of 5 Kgs. Which one will be safer?
Off course, smaller the package safer it would be to transport.
Limited quantity and excepted quantity specifies the size of the small packings.
Limited quantity specifies the maximum quantity that can be in the inner packaging for transporting these DGs under limited quantity.
In the IMDG Code, Look for the dangerous good that needs to be transported and under 7a, it will show the limited quantity for that DG.
If the limited quantity is mentioned as 0, this means that this DG cannot be carried as "limited quantity".
If the limited quantity is mention as 1 liter, this means that maximum quantity in the inner packing needs to be 1 liter.
These small packing of 1 liters need to be packed in one single outer packing. The maximum size of the outer packing needs to be less than 30 Kgs (20 kgs if shrink packed).
If you see under the excepted quantity (column 7b), there are codes like E0 and E1. These codes signify the maximum quantities in the inner and outer packing for that DG to be carried under excepted quantity.
But you know it is much cheaper to have 200 kgs or 500 kgs of DG to be packed in one packing than to pack in smaller packs as per limited or exempted quantity.
Then why would shipper use the provisions of limited or excepted quantity?
That is because IMDG code grants exemptions to some of the requirements if the goods are packed in limited quantity or excepted quantity.
For example, the segregation requirements as per IMDG are not applicable to the Dangerous Goods packed as per limited or excepted quantity.