Most dangerous goods fly legally every day: paints, batteries, aerosols, dry ice, medical samples. What makes them safe is a naming system that leaves nothing to guesswork, and this lesson teaches that system: the vocabulary, the rulebook behind the rulebook, the nine classes and their labels, and the loading rules that keep chemical enemies apart. The next lesson takes the operator's machinery: the approval, the acceptance checks, the crew's paperwork and the reports.
The words of the trade
Seven definitions carry the chapter. Dangerous goods are articles or substances capable of posing a risk to health, safety, property or the environment, and which are shown in the list of dangerous goods in the technical instructions or are classified according to those instructions. A dangerous goods accident is an occurrence associated with and related to the transport of dangerous goods by air which results in fatal or serious injury or major property damage. A dangerous goods incident is an occurrence other than an accident, associated with and related to that transport, not necessarily occurring on board, resulting in injury, property damage, fire, breakage, spillage, leakage of fluid or radiation, or other evidence that the packaging's integrity has not been maintained; and any occurrence that seriously jeopardises the aircraft or its occupants counts as an incident too. An exemption is an authorisation other than an approval, granted by an appropriate national authority, providing relief from the provisions of the Technical Instructions. Packaging means the receptacles and any other components or materials necessary for the receptacle to perform its containment function. A UN number is the four-digit number assigned by the United Nations Committee of Experts to identify a substance or a particular group of substances. And incompatible describes the pairing the stowage rules exist to prevent: dangerous goods which might react dangerously one with another, in the annex's own words.
The instructions behind the annex
Annex 18 is deliberately short, because the detail lives one shelf lower: the detailed provisions for the transport of dangerous goods by air are contained in the Technical Instructions for the Safe Transport of Dangerous Goods by Air, ICAO Doc 9284, approved and issued periodically under the Council's procedure. The operations rules bind the pair together: the transport of dangerous goods by air shall be conducted in accordance with Annex 18 as amplified by the Technical Instructions, including their supplements and addenda. One crew duty from that world belongs to this lesson: if an in-flight emergency occurs, the pilot-in-command shall, as soon as the situation permits, inform the appropriate ATS unit, for the information of aerodrome authorities, of any dangerous goods on board, as provided for in the Technical Instructions. The fire crews meeting the aircraft deserve to know what is burning.
Nine classes of trouble
Classification is the Technical Instructions' job, and the classes are the ones recommended by the United Nations Committee of Experts: nine of them, some subdivided. Class 1 is explosives, its divisions running from mass-explosion hazard (1.1) down to extremely insensitive articles (1.6). Class 2 is gases: flammable (2.1), non-flammable non-toxic (2.2), toxic (2.3). Class 3 is flammable liquids. Class 4 is flammable solids and their cousins: flammable solids with the self-reactive substances, solid desensitised explosives and polymerising substances (4.1), substances liable to spontaneous combustion (4.2), and substances which in contact with water emit flammable gases (4.3). Class 5 is oxidising substances (5.1) and organic peroxides (5.2). Class 6 is toxic (6.1) and infectious (6.2) substances. Class 7 is radioactive material. Class 8 is corrosives. Class 9 is miscellaneous, including environmentally hazardous substances. And one sentence of the system is examinable on its own: the numerical order of the classes and divisions is not the order of the degree of danger.
The dangerous goods list is where the system meets a real shipment: dangerous goods are assigned UN numbers and proper shipping names according to their hazard classification and composition, and the list is used to identify an article by that name and number and to read what applies to it. The marking rules carry the identity onto the box: each package shall be marked with the proper shipping name of its contents and, when assigned, the UN number, and each package shall be labelled with the appropriate labels per the Instructions. The labels themselves are diamonds with a grammar: the hazard symbol in the upper half, the class or division number in the bottom corner, and a colour that codes the hazard: the exploding bomb on orange for Class 1, the flame on red for flammable gases and liquids, the gas cylinder on green for non-flammable, non-toxic gases, the skull and crossbones on white for toxic, the flame over a circle on yellow for oxidisers, the trefoil for radioactive material, the corrosion-damage symbol on white over black for Class 8, and seven vertical stripes for Class 9.