4.1 Package Hazard Labels and Handling Marks

4.1 Package Hazard Labels and Handling Marks

Quick Answer: ADR Chapter 5.2 establishes rigorous visual warning systems for packaged dangerous goods. Hazard warning labels are diamond-shaped (100x100 mm) with an inner line approximately 5 mm from the edge, communicating primary and subsidiary risks. Specialized handling marks—including orientation arrows on two opposite vertical sides, cryogenic handling marks, and red-bordered lithium battery marks—provide vital handling safeguards. Overpacks must display 12 mm 'OVERPACK' text and duplicate all internal markings unless visible through clear wrap, while UN package specification codes encode packaging type, packing group performance (X, Y, Z), mass limits, and manufacturing approval.

ADR 5.2.2 Hazard Warning Labels: Dimensions, Geometry, and Construction

Under ADR 5.2.2, any package containing dangerous goods must display standardized hazard warning labels to alert transport workers, drivers, and emergency responders to the chemical risks inside.

The physical design of hazard warning labels must conform to precise regulatory criteria:

• Diamond Geometry: Labels are diamond-shaped (a square set at an angle of 45°).
• Standard Dimensions: The minimum external dimensions are 100 mm by 100 mm. For small cylinders or small packages where surface area is insufficient, labels may be reduced proportionally if their elements remain clearly visible; Class 2 cylinders have specific ISO 7225 provisions. ADR does not set a universal 50 mm minimum for every reduced hazard label.
• Inner Border Line: A continuous line runs parallel to the perimeter, located approximately 5 mm inside the outer edge; unspecified features follow the model’s proportions.
• Symbol and Text Placement: The upper half of the label displays the pictorial hazard symbol (e.g., flame, skull and crossbones, bursting bomb, oxidizing flame over circle, or acid corroding metal and hands). The lower half contains descriptive text (optional under ADR, mandatory under certain domestic or modal rules) and the mandatory class or division number in the bottom corner.
• Durability and Weather Resistance: Under ADR 5.2.2.2.1.7, labels must withstand exposure to open weather conditions without a substantial reduction in their effectiveness. Do not import a maritime durability test into ADR as a universal road-label requirement; follow the applicable mode’s rules.

Primary Hazard Labels vs. Subsidiary Hazard Labels

Dangerous goods frequently present multiple intersecting hazards. ADR addresses this through primary and subsidiary hazard classification:

• Primary Hazard Label: Identifies the principal risk category assigned to the substance based on the classification criteria of Part 2. It always features the class or division number in the bottom corner (e.g., '3' for flammable liquids, '8' for corrosives, '6' for toxic substances).
• Subsidiary Hazard Label: Required when a substance poses one or more secondary hazards identified in Column (5) of dangerous goods Table A in Chapter 3.2. Examples include:
  • Methanol (UN 1230): Class 3 flammable liquid with a Class 6.1 toxic subsidiary hazard. Packages require both a Class 3 label and a Class 6.1 label.
  • Nitric acid, red fuming (UN 2032): Class 8 corrosive substance with Class 5.1 oxidizing and Class 6.1 toxic subsidiary hazards.
• Regulatory Equivalence: In current ADR regulations, subsidiary hazard labels also show the hazard class number in the bottom corner. For drivers and handlers, subsidiary hazards carry identical operational significance to primary hazards: they enforce mandatory personal protective equipment, emergency escape masks, and mixed loading prohibitions under ADR 7.5.2.

Mandatory Handling and Warning Marks

Beyond hazard class diamonds, ADR Chapter 5.2 specifies critical handling marks:

Orientation Arrows (ADR 5.2.1.10)

Package orientation arrows indicate the correct upright positioning of packages during storage, handling, and transit:

• Design: Two black or red arrows pointing upward on a white or contrasting rectangular background, with or without a surrounding frame. Use a clearly visible size commensurate with the package; ADR does not prescribe a universal 74 × 105 mm minimum for these arrows.
• Mandatory Applications: Orientation arrows are legally required on:
  1. Combination packagings having inner packagings containing liquid dangerous goods.
  2. Single packagings fitted with vents (such as vented drums or jerricans).
  3. Closed or open cryogenic receptacles for refrigerated liquefied gases.
  4. Specified machinery/apparatus containing liquids where orientation is needed (SP 301).

Check the exceptions in 5.2.1.10.2; for example, certain hermetically sealed inner packagings do not require arrows.

• Placement Rule: Arrows must be displayed on two opposite vertical sides of the package, pointing correctly upright.
• Prohibited Uses: ADR 5.2.1.10.2 lists exemptions from mandatory arrows, including specified small inner packagings and hermetically sealed inners. Under 5.2.1.10.3, arrows for purposes other than indicating orientation must not be displayed on a package marked under this subsection. “Not required” does not mean orientation arrows are forbidden on every other package.

Cryogenic Liquid Handling Mark

Cryogenic receptacles carrying refrigerated liquefied gases (Class 2, classification codes beginning with 3) present severe hazards of frostbite, rapid liquid expansion, and pressure build-up. In addition to Class 2.2 non-flammable non-toxic gas labels, warning marks or cryogenic warning instructions indicate that containers must remain upright and vented to avoid catastrophic rupture.

Lithium Battery Mark (ADR 5.2.1.9)

Small lithium metal (UN 3090, UN 3091) and lithium ion (UN 3480, UN 3481) cells and batteries transported under Special Provision 188 must bear the standardized lithium battery mark:

• Design: A rectangle with a red hatched border (hatching width at least 5 mm).
• Symbol: A black graphic showing a group of batteries with one damaged and emitting flames.
• UN Numbers: Must display the applicable UN number(s) preceded by the letters 'UN' (e.g., 'UN 3480') with all features clearly visible and in the model’s proportions.
• Dimensions: Minimum 100 mm wide by 100 mm high. Where package dimensions require, a reduced size of 100 mm wide by 70 mm high is permitted.

Overpack Marking Rules (ADR 5.1.2.1)

An overpack is an enclosure used by a single consignor to consolidate one or more packages into a single handling unit, such as several boxes stacked on a wooden pallet and bound with plastic stretch wrap, or packages placed in a protective outer crate.

Under ADR 5.1.2.1, overpacks are subject to strict marking obligations:

1. The Word 'OVERPACK': The overpack must be clearly marked with the capital letters 'OVERPACK' at least 12 mm high. The word must be in an official language of the country of origin, and if that language is not English, French, or German, also in English, French, or German.
2. Replication of Labels and UN Numbers: Every hazard label (primary and subsidiary), UN number (preceded by 'UN'), and handling mark (such as orientation arrows or environmentally hazardous marks) present on the enclosed packages must be reproduced visibly on the exterior of the overpack.
3. Visibility Exemption: If all hazard labels, UN numbers, and handling marks on the individual packages inside the overpack remain completely and clearly visible from the outside (for example, beneath transparent shrink wrap), neither the word 'OVERPACK' nor duplicate external markings are required.

UN Specification Packaging Marks: Structure and Decoding

Packagings subject to Chapter 6.1 design-type testing carry the required UN mark. Other containment types and specific exemptions have different provisions. The applicable tests depend on the design and contents; not every box undergoes a hydraulic-pressure test.

Source check: 17 October 2026 — ADR 2025, English text published by the Slovak Ministry of Transport, 5.2 and 6.1.3.