Marking, labelling & placarding

Packages must show the UN number and the hazard label (the diamond) for each danger. The diamond shows the hazard symbol on top and the class number in the bottom corner. If the goods have a second danger, a subsidiary diamond is added (without the class number). Some packages also need an orientation arrow (this way up) or the environmentally hazardous mark (dead fish and tree).

Label = a diamond: symbol on top, class number in the bottom corner.

Vehicles carrying dangerous goods show plain orange rectangular plates front and rear. In some cases (tanks, bulk) the plate carries numbers: a Hazard Identification Number on top (the 'Kemler' code) and the UN number below. Larger placards — the same diamond as the package label but bigger — go on tanks and containers so the class is visible from outside. When you no longer carry dangerous goods, the plates/placards must be removed or covered.

Plain orange plates front and rear for packaged goods above the threshold.

On tankers and bulk loads the orange plate is the at-a-glance summary. The top number is the Hazard Identification Number (commonly called the Kemler code) and tells you the danger in one to four digits. The first digit is the main class (3 = flammable liquid, 8 = corrosive). A repeated digit means an intensified hazard (33 = highly flammable). An 'X' at the front means 'reacts dangerously with water — do not use water'. Below it is the UN number. So a plate showing 33 / 1203 means highly flammable liquid, UN1203 petrol.

Top = Hazard ID (Kemler); bottom = UN number.

Where a tank, container, swap-body or compartmented vehicle is carrying dangerous goods, the same diamond used on packages appears as an enlarged 250 mm × 250 mm placard on each side and the rear. A compartmented tank with different products in each compartment needs each compartment's placard fitted alongside the relevant orange plate showing that compartment's HIN/UN. The driver doesn't fit these — but you DO check they are present and correct before driving away. Missing or wrong placards is an enforcement-stop issue.

Enlarged placards (≥250 mm) on both sides and rear of tanks/containers.

On a pre-trip walk-round, look out for: (1) Orange plates still showing from yesterday's load when today's vehicle is empty — that's a 'remove or cover' breach. (2) A subsidiary-hazard label that's torn, faded or missing. (3) The wrong UN number on the orange plate vs the paperwork — even one digit out matters. (4) Marked packaging stowed with the labels facing the wall so emergency services can't read them. If you find any of these, fix it (cover the plate) or refuse to drive until it's sorted, and tell the office.

Old plates showing on an empty vehicle = 'remove or cover' breach.

Two extra marks you may see: (1) The 'red triangle with a thermometer' is the elevated-temperature mark — used when a liquid is carried at ≥100 °C or a solid at ≥240 °C (think hot bitumen, UN3257). It tells crews and the emergency services the load is HOT — don't open, beware of pressurised release on rupture. (2) The fish-and-tree symbol is the environmentally hazardous substance mark — keep spills out of drains and watercourses. You may also see the 'this way up' arrows on packages of liquids in inner containers; respect them when handling.

Elevated-temperature mark = a red triangle with a thermometer (5.3.3).