Chemical labels are the frontline of hazard communication. Under the UK’s retained GB CLP framework, pictograms and signal words are not design elements or best-practice suggestions. They are mandatory indicators that communicate the nature and severity of hazards at a glance. Regulators treat them as safety controls, not supplementary information. If they are missing, incorrect, or outdated, the label is considered non-compliant even if other hazard details are present elsewhere.
How GHS Pictograms Are Assigned
GHS pictograms are applied based on the hazard classification of a substance or mixture. Each pictogram corresponds to specific hazard classes and categories, such as flammability, acute toxicity, corrosion, or long-term health effects. Where multiple hazards apply, more than one pictogram may be required on a single label. The absence of a required pictogram is a clear breach of GB CLP, regardless of whether the hazard is described in text. Pictograms must always reflect the current classification, not historical or assumed risk profiles.
Understanding Signal Words and Severity
Signal words work alongside pictograms to indicate severity. Only two signal words are permitted under GHS: “Danger” and “Warning.” “Danger” is used for the most severe hazard categories, while “Warning” applies to lower categories. Only one signal word may appear on a label, even if multiple hazards are present. In those cases, the signal word linked to the highest severity hazard must be used. Applying both signal words, or selecting the wrong one, is a common compliance failure.
Common Errors Triggered by Classification Changes
Many pictogram and signal word errors arise when classifications change but labels are not updated. Mandatory updates, such as those introduced through amendments to the GB Mandatory Classification and Labelling List, often require pictograms to be added, removed, or upgraded, and signal words to change accordingly. A substance may move from “Warning” to “Danger” without any change in how it is used. If the label is not updated by the compliance deadline, the product cannot legally be placed on the market.
Mixture Labels and Downstream Impacts
Mixture labels are particularly vulnerable to error. Pictograms and signal words for mixtures are determined through calculation rules based on ingredient hazards and concentrations. A reclassification of a single component, or a minor formulation adjustment, can change the required pictograms for the entire product. If mixture labels are not reassessed after upstream changes, outdated hazard communication can remain in circulation even when formulations appear unchanged.
Layout, Size, and Space Constraints
GB CLP sets minimum size and visibility requirements for pictograms and signal words. They must be prominent, clearly legible, and not reduced to accommodate other content. On small containers, this can create layout pressure, especially when multiple pictograms are required. In regulated sectors, extended content or multi-layer labels are often used to preserve legibility while ensuring all mandatory elements remain compliant.
Keeping Chemical Labels Compliant Over Time
Pictograms and signal words should always be treated as outputs of classification, not fixed design features. Any regulatory update or formulation change should trigger a label review. This approach reduces the risk of outdated hazard communication and helps ensure chemical labels remain compliant with GB CLP as requirements evolve.