Dangerous goods are those having inherent nature to cause harm to living things, other goods and means of transport or environment. There are stringent regulations for carriage of dangerous goods through different modes of transport. For transport purpose dangerous goods are classified into nine different classes basis the hazard they pose during transport.
Dangerous Goods Classes
Class 1: Explosives
Division 1.1: substances and articles which have a mass explosion hazard
Division 1.2: substances and articles which have a projection hazard but not a mass explosion hazard
Division 1.3: substances and articles which have a fire hazard and either a minor blast hazard or a minor projection hazard or both, but not a mass explosion hazard
Division 1.4: substances and articles which present no significant hazard
Division 1.5: very insensitive substances which have a mass explosion hazard
Division 1.6: extremely insensitive articles which do not have a mass explosion hazard
Class 2: Gases
Class 2.1: flammable gases
Class 2.2: non-flammable, non-toxic gases
Class 2.3: toxic gases
Class 3: Flammable liquids
Class 4: Flammable solids; substances liable to spontaneous combustion; substances which, in contact with water, emit flammable gases
Class 4.1: flammable solids, self-reactive substances, solid desensitized explosives and polymerizing substances
Class 4.2: substances liable to spontaneous combustion
Class 4.3: substances which, in contact with water, emit flammable gases
Class 5: Oxidizing substances and organic peroxides
Class 5.1: oxidizing substances
Class 5.2: organic peroxides
Class 6: Toxic and infectious substances
Class 6.1: toxic substances
Class 6.2: infectious substances
Class 7: Radioactive material
Class 8: Corrosive substances
Class 9: Miscellaneous dangerous substances and articles
Dangerous goods are transported through three modes, pipeline, bulk vessels and in packaged form. Dangerous goods in packaged form is transported by rail, road, river, air and sea. The United Nations Model Regulations, Recommendations on the Transport of Dangerous Goods lays down the guidelines for classification, packaging, marking and labeling of packages, marking and placarding of cargo transport units and dangerous goods transport documents.
Packaged form means the form of containment specified in the transport regulations.
Package and packaging are two different things. Package means the complete product of the packing operation, consisting of the packaging and its contents prepared for transport. Packaging means one or more receptacles and any other components or materials necessary for the receptacles to perform their containment and other safety functions.
Dangerous goods must be packed in good quality packagings which must be strong enough to withstand the shocks and loadings normally encountered during transport, including trans-shipment between cargo transport units and between cargo transport units and warehouses as well as any removal from a pallet or overpack for subsequent manual or mechanical handling. Packagings must be constructed and closed so as to prevent any loss of contents when prepared for transport which may be caused under normal conditions of transport, by vibration, or by changes in temperature, humidity or pressure (resulting from altitude, for example). Packagings must be closed in accordance with the information provided by the manufacturer. No dangerous residue shall adhere to the outside of packages during transport.
For packing purposes, substances other than those of classes 1, 2, 5.2, 6.2 and 7, and other than self-reactive substances of class 4.1, are assigned to three packing groups in accordance with the degree of danger they present:
Packing group I: substances presenting high danger;
Packing group II: substances presenting medium danger; and
Packing group III: substances presenting low danger.
Provisions for packagings are based on the packagings currently used. All packagings intended to carry dangerous goods in transport must be certified to meet the United Nations performance requirement.
Depending on the packing group of the dangerous goods the drop test height of packaging varies.
If substances to be transported have a relative density exceeding 1.2, the drop height must be calculated on the basis of the relative density (d) of the substance to be carried, rounded up to the first decimal, as follows:
Dangerous goods may be in physical form, solid, liquid or gas. The function of packaging is to contain the dangerous goods without leakage or exposure under normal conditions of transport.
Following are the kind of packagings and materials used
An example of packing codes
The rational used for assigning types of packagings, types of material used and maximum quantity per packaging is based on the dangerous goods in question and its nature of hazard. A dangerous goods in same class but differing in packing group will have different types of packagings and or maximum quantity permitted per packaging authorized by the regulation.
Authorized packaging for each dangerous goods entry is listed through Packing Instructions in dangerous goods list with symbol “P” and a code, example Packing instruction P100. Also, additional packing provisions when assigned will be indicated through packing provision symbol PP, example PP5 (PP5: For UN 1204, packagings shall be so constructed that explosion is not possible by reason of increased internal pressure. Gas cylinders and gas receptacles shall not be used for these substances).
Most low hazard liquid and solid dangerous goods are assigned with packing instruction P001 and P002 respectively. Otherwise the rational used for assigning packagings through packing instructions are based on hazard classification.
An example packing instruction
Class 1 Explosives: Packing instructions P100s
Classification of explosives takes into consideration of its intrinsic hazard nature and possible effects due to over confinement, example metal packagings. All packagings of class 1 explosives are to meet the packing group II performance level.
Class 2 Gases: Packing instructions P200s
Class 3 Liquid Desensitized explosives P300s
Class 4 Flammable solids, pyrophoric substances… P400s
Other than self-reactive substances of class 4.1 many class 4 substances are assigned to P400 series of packing instructions.
Class 5 oxidizing substances and organic peroxides P500s
Chemical oxygen generators are assigned to P500 and stabilized hydrogen peroxide to P501. P520 is assigned to various types of self-reactive substances under class 4.1 and organic peroxides of class 5.2
Class 6.1 Toxic Substances P600s
Tear gas candles and toxic ammunitions are assigned to P600
Class 6.2 Infectious substances
Infectious substances are assigned to P620, P621 or P650
Class 7 Radioactive materials
No packaging instructions are assigned for radioactive materials. Packagings for radioactive materials are authorized by International Atomic Energy Agency (IAEA).
Class 8 Corrosive substances P800s
P800 to P804 are assigned to various corrosive substances
Class 9 Miscellaneous dangerous goods P900s
Certain class 9 dangerous goods are assigned to specific packing instructions in P900 series. Example fishmeal, chemical kit, lithium batteries etc.