A ?grigid outer packaging?h means simply a hard outer package, i.e., it would not have to be a UN specification Mar ed outer packaging. It is more or less a strong Overpack having the required flame penetration and thermal resistance features.
As you know, the cylinder itself is a UN certified outer package. The US rule requires the shipper to protect the UN certified cylinder in a ?grigid outer packaging?h having the flame penetration and thermal resistance features. So it is 100% an Overpack.
The DGD should be made, such as:
1 steel cylinder x 2kg
OVERPACK used x 3
If the ?grigid outer packaging?h carries a UN packaging specification Mar , then the shipment can be Dec ared as a Combination package, and May be Dec ared, such as:
3 wooden boxes x 2kg