This part of ISO 20421 specifies operational requirements for large transportable vacuum-insulated cryogenic vessels of more than 1 000 l volume. The scope includes putting into service, filling, withdrawal, transport within the location, storage, maintenance, periodic inspection and emergency procedures. For the transport of these vessels by public road, rail, waterway, sea and air, additional requirements may apply; these are defined in specific regulations. This part of ISO 20421 applies to vessels for cryogenic fluids as specified in ISO 20421-1. The additional requirements for flammable fluids are detailed in Clause 16.