RiskAssess

Classes of Dangerous Goods

Dangerous Goods are divided into Classes, depending on the type of dangerous properties that they possess. For instance, all the flammable liquids are placed in the same Class.

We use the United Nations (UN) classification system, with a total of nine classes [1]. Many of the Classes are further divided into Subclasses. Fortunately, substances in some of the Subclasses are not found in schools, and are not relevant. The Classes and Subclasses of Dangerous Goods found in schools are listed in Table 1.

When a chemical is taken out of storage and used in a laboratory, the requirements of the GHS (Globally Harmonized System of Classification and Labelling of Chemicals) must be followed [2]. There are thus two systems applicable to chemicals in schools:

Don’t confuse the pictograms for GHS [2,3] with the hazard labels for Dangerous Goods [4]. The hazard labels are distinguished by the number of the Class at the bottom of the diamond.

Table 1

The Classes, Subclasses and Packing Groups (PG) of Dangerous Goods, their placarding quantities and examples of goods in each category.

Dangerous Goods are mostly chemicals, but the term includes biological materials in Class 6 that are "infectious substances" (hopefully, not found in schools) and "radioactive materials" in Class 7 (only minute amounts found in schools). The goods are listed in the Dangerous Goods legislation of each country, based on a United Nations list.

Dangerous Goods legislation covers both transport and storage, since storage is regarded as an intermediate stage of transport. Schools are rarely involved in the transport of Dangerous Goods. Transport might occur during the transfer of chemicals from one school campus to another, on a field Science excursion, or during collection of LPG cylinders, dry ice, etc. In these cases, the Dangerous Goods requirements should be followed.

Schools store small quantities of many Dangerous Goods in Science, Art, Technology, Maintenance and other areas. Sometimes larger quantities of goods such as LPG, diesel, fuel oil, pool chlorine, etc may be stored and must comply with regulations.

Subsidiary risk

A classified substance may have more than one dangerous property. For instance, acetic acid is both corrosive and flammable. It is therefore classified as a Class 8 corrosive substance with a Subsidiary Risk 3 for its flammability, usually written Class 8/3. Storage requirements for both the Dangerous Goods Class and the Subsidiary Risk should be followed, with priority given to the primary risk.

Manufactured products

The term "manufactured product" is used to refer to a chemical mixture that contains a large proportion of flammable liquids and at least 10% solid material. Examples are paints, varnishes, lacquers, polishes and adhesives. Although these products are flammable, they are not counted along with other flammable liquids (Class 3) for determining whether notification of Dangerous Goods storage is required, provided that they are stored in the original containers of the correct size. However, these products must be stored and transported in the same way as other Class 3 Dangerous Goods. Manufactured products are usually Class 3 PG II or Class 3 PG III. Paints are not required to be stored in a flammable liquids cabinet (but it is a good idea to do so).

Not classified as Dangerous Goods

Many chemicals are not classified as Dangerous Goods, but this does not mean that they are without hazardous properties. It just means that their hazardous properties, if any, do not pose a danger for the transport and storage of the chemicals. Consult the GHS information for each chemical to determine the hazards that may arise when using the chemical.

Placarding quantities

Quantities of dangerous goods in excess of the quantities in Table 1 require special signage, called "placarding". This involves installing HAZCHEM signs and other actions to ensure that emergency services (amongst others) know what is stored at the various storage locations. A school should not store such large quantities of chemicals that placarding is required, except for LPG, diesel and, occasionally, for pool chlorine.

Quantities of Dangerous Goods 2-10 times greater than the placarding quantities are known as "manifest quantities"; their quantities must be notified to the appropriate authority and special requirements apply for safe storage.

Chemical register

A school is required by law to keep an up-to-date list of the chemicals in each storage location. The chemical register must be updated, so that it remains current at all times. The exact frequency of updates is not defined in legislation.

For further information regarding Dangerous Goods and their storage, please see ‘Safety In Schools’, Chapter C4 [5].