The IMO International Gas Carrier Code, became mandatory in 1986.

The requirements of this code are incorporated in the rules for ships carrying liquefied gases published by Lloyd’s and other classification societies.

The code covers damage limitations to cargo tanks and ship survival in the event of collision or grounding, ship arrangements for safety, cargo containment and handling, materials of construction, environmental controls, fire protection, use of cargo as fuel etc. Of particular interest in the context of ship construction is the section of cargo containment which defines the basic cargo container types and indicates if a secondary barrier is required, i.e. a lining outside the cargo containment which protects the ships hull structure from the embrittling effect of the low temperature should cargo leak from the primary tank structure. The cargo containment types are described next.