Dangerous goods are solids, liquids, or gases that can harm people, other living organisms, property, or the environment. They are often subject to chemical regulations. The most widely applied regulatory scheme is that for the transportation of dangerous goods. The United Nations Economic and Social Council issues the UN Recommendations on the Transport of Dangerous Goods, which form the basis for most regional and national regulatory schemes. 

Dangerous goods are divided into nine classes (in addition to several subcategories) on the basis of the specific chemical characteristics producing the risk:

• Class1: Explosives
  • 1.1-Substances and articles which have a mass explosion hazard.
  • 1.2-Substances and articles which have a projection hazard but not a mass explosion hazard.
  • 1.3-Substances and articles which have a fire hazard and either a minor blast hazard or a minor projection hazard or botd, but not a mass explosion hazard.
  • 1.4-Substances and articles which present no significant hazard.
  • 1.5-Very insensitive substances which have a mass explosion hazard.
  • 1.6-Extremely insensitive articles which do not have a mass explosion hazard.
• Class 2-Gases: Compressed, Liquefied or Dissolved under Pressure
  • 2.1-Flammable gases
  • 2.2-Non-Flammable gases
  • 2.3-Toxic gases
• Class 3-Flammable Liquids
• Class 4-Flammable Solids or Substances
  • 4.1-Flammable solids
  • 4.2-Substances liable to spontaneous combustion
  • 4.3-Substances which, in contact with water, emit flammable gases.
• Class 5-Oxidizing Substances (agents) and Organic Peroxides
  • 5.1-Oxidizing substances (agents) by yielding oxygen increase the risk and intensity of fire
  • 5.2-Organic peroxides - most will burn rapidly and are sensitive to impact or friction
• Class 6-Toxic and infectious Substances
  • 6.1-Toxic substances
  • 6.2-Infectious substances
• Class 7-Radioactive Substances
• Class 8-Corrosives
• Class 9-Miscellaneous dangerous substances and articles (Marine pollutants which are not of an otherwise dangerous nature are listed in class 9)
• MHB-Materials hazardous only in bulk (The regulations for materials hazardous only in bulk are not applicable to these materials when they are carried in closed freight containers, however, many precautions may have to be observed)