All substances of an inflammable nature which are liable to spontaneous combustion either in themselves or when stowed next to other substances and, when mixed with air, are liable to generate explosive gases or produce suffocation or poisoning or tainting of foodstuffs.
The International Maritime Dangerous Goods Code (IMDG Code) lists over 3000 hazardous substances. Goods can be categorized as dangerous for any of the following reasons:
- Because they require special care and handling in transit.
- Because their properties are harmful to human life.
- Because they possess qualities or create risks that could expose the carrier to liabilities or losses neither acknowledged nor agreed in the contract of carriage.
- Because they could cause damage to the ship holds or machinery.
- Because their properties require excessive expenditure by the carrier to guarantee safe transport.
- Because, if they escape from the ship, they are likely to cause environmental damage.
The environmental aspect is the most frequently quoted when cargoes are classified as hazardous or noxious.