According to the European agreement “International Agreement on Dangerous Goods ADR” the goods are classified into 9 types according to their Class from 1 to 9. These are.     Class 1_ Explosives: 1.1 Materials with the danger of causing a mass explosion. 1.2 Materials with risk of projection. 1.3. Materials with a risk of causing a light fire. 1.4. Materials with a slight risk of explosion in case of burning. 1.5. Materials that are not very sensitive to the mass explosion. 1.6. Materials extremely insensitive to an explosion.   Class 2_ Gases: with three subdivisions:                        2.1 Flammable gases when in contact with heat.                        2.2 Flammable and non-toxic gases.                        2.3 Toxic gases by inhalation.   Class 3_ Flammable liquids: gasoline, white spirit or paints.   Class 4_Flammable solids: we find three subcategories.                       4.1 Flammable solids under normal conditions.                       4.2 Substances that can become heated and spontaneously ignite.                      4.3 Substances that, when in contact with water, can ignite.   Class 5_Comburent and organic peroxides:                     5.1 Oxidizing substances: materials that, when in contact with others, can cause a fire.                     5.2 Organic peroxides: very dangerous substances that can cause an explosion.   Class 6_Toxic and infectious.                     6.1 Toxic substances: contact with them can cause death.                     6.2 Infectious substances: their microorganisms can cause diseases.   Class 7_Radiactive: those with radioactive elements, such as uranium or plutonium.  Class 8_Corrosive: when in contact with them they damage the skin and if they are ingested or inhaled they can cause poisoning. Sulfuric acid or sodium hypochlorite.   Class 9_Substances and various objects: others that are not included in the previous points. An example: is dry ice, which is used to refrigerate products.