The physical separation of incompatible dangerous goods in stowage to prevent hazardous reactions if packaging fails.
In practice
The chief mate applies segregation requirements when drawing up the dangerous goods stowage plan. Incompatible cargoes such as explosives and flammable liquids, or acids and bases, must be stowed so that the required category of separation is maintained throughout the voyage, accounting for the ship's layout and the actual positions of each consignment. On container ships, automated stowage planning software cross-checks the segregation matrix during loading plan preparation. The OOW should be aware of the IMDG segregation categories and the positions of any dangerous goods on board, particularly when a fire or casualty may involve adjacent cargo of a different class. Failure to comply with IMDG segregation requirements is a Class I deficiency in Port State Control inspections.
Regulatory detail & full definition
Segregation of dangerous goods is the practice of physically separating incompatible hazardous cargoes in stowage to prevent dangerous reactions—fire, explosion, toxic gas generation, or corrosive damage—if packaging fails or cargo leaks. The IMDG Code Chapter 7.2 defines four degrees of segregation: 'away from' (minimum separation), 'separated from', 'separated by a complete compartment or hold from', and 'separated longitudinally by an intervening complete compartment or hold from'. A Segregation Table in the Code specifies the required segregation category for each combination of IMDG classes.
The chief mate applies segregation requirements when drawing up the dangerous goods stowage plan. Incompatible cargoes such as explosives and flammable liquids, or acids and bases, must be stowed so that the required category of separation is maintained throughout the voyage, accounting for the ship's layout and the actual positions of each consignment. On container ships, automated stowage planning software cross-checks the segregation matrix during loading plan preparation. The OOW should be aware of the IMDG segregation categories and the positions of any dangerous goods on board, particularly when a fire or casualty may involve adjacent cargo of a different class. Failure to comply with IMDG segregation requirements is a Class I deficiency in Port State Control inspections.