Dangerous goods, also called hazardous materials or HazMat ("HazMat teams" are personnel specially trained to handle 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. Dangerous goods include materials that are radioactive, flammable, explosive, corrosive, oxidizing, asphyxiating, biohazardous, toxic, pathogenic, or allergenic. Also included are physical conditions such as compressed gases and liquids or hot materials, including all goods containing such materials or chemicals, or may have other characteristics that render them hazardous in specific circumstances.

Dangerous goods are often indicated by diamond-shaped signage. The colours of each diamond in a way has reference to its hazard ie: Flammable = red, Explosive = orange, because mixing red (flammable) with yellow (oxidising agent) creates orange. Non Flammable Non Toxic Gas = green, due to all compressed air vessels being this colour in France after World War II. France is where the diamond system of HazMat identification originated.

Mitigating the risks associated with hazardous materials may require the application of safety precautions during their transport, use, storage and disposal. Most countries regulate hazardous materials by law, and they are subject to several international treaties as well. Even so, different countries may use different class diamonds for the same product. For example, in Australia, Anhydrous Ammonia UN 1005 is classified as 2.3 (Toxic Gas) with sub risk 8 (Corrosive), where as in the U.S. it is only classified as 2.2 (Non Flammable Gas).

Persons who handle dangerous goods will often wear protective equipment, and metropolitan fire departments often have a response team specifically trained to deal with accidents and spills. Persons who may come into contact with dangerous goods as part of their work are also often subject to monitoring or health surveillance to ensure that their exposure does not exceed occupational exposure limits.

Laws and regulations on the use and handling of hazardous materials may differ depending on the activity and status of the material. For example, one set of requirements may apply to their use in the workplace while a different set of requirements may apply to spill response, sale for consumer use, or transportation. Most countries regulate some aspect of hazardous materials.

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. For instance, the International Civil Aviation Organization has developed regulations for air transport of hazardous materials that are based upon the UN Model but modified to accommodate unique aspects of air transport. Individual airline and governmental requirements are incorporated with this by the International Air Transport Association to produce the widely used IATA Dangerous Goods Regulations. Similarly, the International Maritime Organization has developed the International Maritime Dangerous Goods Code ("IMDG Code", part of the International Convention for the Safety of Life at Sea) for transportation on the high seas, and the Intergovernmental Organisation for International Carriage by Rail has developed the Regulations concerning the International Carriage of Dangerous Goods by Rail ("RID", part of the Convention concerning International Carriage by Rail). Many individual nations have also structured their dangerous goods transportation regulations to harmonize with the UN Model in organization as well as in specific requirements.

The Globally Harmonized System of Classification and Labeling of Chemicals or GHS is an internationally agreed upon system set to replace the various different classification and labeling standards used in different countries. The GHS will use consistent criteria for classification and labeling on a global level.

Dangerous goods are divided into classes on the basis of the specific chemical characteristics producing the risk.

Note: The graphics and text in this article representing the dangerous goods safety marks are derived from the United Nations-based system of identifying dangerous goods. Not all countries use precisely the same graphics (label, placard and/or text information) in their national regulations. Some use graphic symbols, but without English wording or with similar wording in their national language. Refer to the Dangerous Goods Transportation Regulations of the country of interest.

For example, see the Dangerous Goods Safety Marks in the Canadian Transportation of Dangerous Goods Regulations.

The statement above applies equally to all the Dangerous Goods classes discussed in this article.

Free Hazchem Guide from The UK National Chemical Emergency Centre (NCEC)