21-09-2016, 03:49 PM
1455602194-ClassesofHazardousChemicals8.09.doc (Size: 1.43 MB / Downloads: 11)
MAJOR GROUPS OF HAZARDOUS CHEMICALS
Currently there are three major groups of hazardous chemicals in Australia - dangerous goods, scheduled drugs & poisons, hazardous substances and chemicals of security concern.
DANGEROUS GOODS – These are materials listed in the Australian Dangerous Goods Code1 or in state or territory dangerous goods legislation. 2 The term ‘dangerous goods’ generally applies to chemicals and materials used in industry that have the potential to be a safety hazard. To some extent the classification of a ‘dangerous good’ depends on its quantity, since the major concern with ‘dangerous goods’ is the risk associated with their bulk transport and storage.
There are 9 classes of dangerous goods, each with a characteristic class number and symbol. Some of these classes are divided into divisions. The classes of dangerous goods can be considered to be listed in the order from most hazardous to least hazardous. A chemical may belong to more than one of these classes, for example glacial acetic acid is classed as both a flammable liquid and a corrosive substance.
Explosives pose a major hazard because of the destruction to people and property caused by their detonation. An explosive, on detonation, undergoes a rapid chemical change with the production of a large gas volume relative to the volume of explosive. It is this rapidly expanding pressure wave that produces the devastating destruction characteristic of explosives. Explosives include: explosive substances, pyrotechnic substances and explosive articles.
The explosive class of dangerous goods is divided into 6 divisions. These sub-classes do not include those explosives that are too hazardous to transport, or substances that are not intrinsically explosive but can form an explosive atmosphere of gas, vapour, or dust.
Division 1.1 Substances that have a mass explosion hazard.
Division 1.2 Substances and articles that have a projection hazard, but not a mass explosion hazard.
Division 1.3 Substances or articles that have a fire hazard and either a minor blast hazard or minor projection hazard, or both, but not a mass explosion hazard.
Division 1.4 Substances and articles that present no significant hazard. The effect would be confined to the package and no projection of fragments of size or range is expected.
Division 1.5 Very insensitive substances that have a mass explosion hazard. These substances have a low probability of initiation or of transition from burning to detonation under normal conditions of transport.
Division 1.6 Extremely insensitive articles that do not have a mass explosion hazard.
Divisions of dangerous goods Class 1 - Explosives
There are a number of potentially explosive chemicals that may be found in the laboratory which are either:
• chemicals that are intrinsically explosive; or
• may become explosive on deterioration.
Lists of intrinsically and potentially explosive chemicals are located in the Explosive Chemicals List Document.
Intrinsically explosive chemicals should NOT be used by staff or students at the ANU (i.e. ordered, stored, handled or disposed of) unless expert advice is received and appropriate practices are in place.
Class 2 - Gases
Gases pose a hazard because of their ability to diffuse over a large volume to exert a flammable, asphyxiating, toxic or oxidising effect.
A gas is defined as a dangerous good if:
• at 50 ˚C has a vapour pressure greater than 300 kPa, or
• it is completely gaseous at 20 ˚C at standard pressure (101.3 kPa).
Gases can be stored compressed, liquefied or dissolved under pressure.
Dangerous goods class 2 is divided into four sub-classes -
Flammable liquids are liquids which are capable of being ignited and burned. They may also be mixtures of liquids, containing solids in solution or suspension (eg. paints).
Ignition of the flammable liquid and production of fire is the major hazard here. The flammable liquids (Class 3) are considered a higher risk than flammable solids (Class 4) because of the:
• generally higher vapour pressure exhibited by liquid compounds,
• ability of the liquid to flow under gravity and collect in low points or flow into drains and waterways.
Flammable liquids are further divided into three Packing Groups (PG) according to the degree of danger they present.
* Liquids that will ignite and burn with a flash point above 60.5 C are classified as combustible liquids
Class 4 - Flammable Solids
Class 4 dangerous goods are flammable solids, and their major hazard is their flammable nature.
Class 4 is divided into three divisions, and the substances within each divisions are assigned to packing group I (highest danger), II (moderate danger), or III (minor danger).
There are three further sub-divisions of class 4.1, which are flammable solids, self-reactive and related substances and desensitized explosives.
Flammable solids are solids that, under conditions encountered in transport, are readily combustible or may cause or contribute to fire through friction. They can also be a powder or paste. An added danger can be from toxic combustion products. eg. metal powders, naphthalene.
Self-reactive and related substances are substances that are liable to undergo a strong exothermic reaction. e.g. aliphatic azo- compounds, organic azides.
Desensitized explosives are substances that may explode if not diluted sufficiently. e.g. ammonium picrate, wetted; dinitrophenol, wetted; barium azide, wetted; nitrocellulose with alcohol.
Organic peroxides all contain the bivalent -O-O- (O22-) structure. They are thermally unstable substances, that may undergo exothermic, self-accelerating decomposition and most substances of this class are combustible. In addition, they may have one or more of the following properties - be liable to:
• explosive decomposition;
• burn rapidly;
• be sensitive to impact or friction;
• react dangerously with other materials; or
• cause damage to the eyes.
Examples of organic peroxides are dibenzoyl peroxide, peracetic acid and perbenzoic acid.
Class 6 – Toxic and Infectious Substances
Class 6 dangerous goods are hazardous because of their chemical toxicity or biological infectivity to people, animals or the environment. The words "toxic" and "poisonous" are synonyms.
Class 6 is divided into two divisions, with the substances in each division being assigned to packing group I (great danger), II (moderate danger), or III (minor danger).