How does ADR 8.1.4 set portable fire-extinguisher capacity on a fully regulated transport unit?

1. One 2 kg dry-powder extinguisher is enough for every vehicle mass
2. Minimum number and total dry-powder (or equivalent) capacity increase with the transport unit’s maximum permitted mass, with at least one extinguisher suitable for a cab or engine fire
3. Extinguishers are optional if the load is Class 9
4. Only a water hose connected to a hydrant at the consignor is accepted