Hazard diamonds

nine pictures, one frame

Unicode: U+2620 ☠ · U+2622 ☢ · the GHS diamonds themselves are not encoded — only some of their interiors are
The job: Tell a worker what a chemical will do to them, on the container, in any country, without depending on the language they read.
Standards: The Globally Harmonized System — the UN “purple book” — implemented as CLP in the European Union and HazCom in the United States. The syntax is the frame: a red-bordered diamond declares this is a GHS chemical hazard, and the black symbol inside declares which of nine classes. Nine interiors, one frame, and an entire continent made to relearn a set when it replaced the older orange squares.
Failure modes: One of the nine is a grab-bag. The exclamation-mark pictogram covers irritation, skin sensitisation, lower-tier acute toxicity and ozone harm, which is close to meaning something, possibly. The health-hazard silhouette — a torso with a starburst in the chest — is poorly recognised without training. And the diamond is also the shape of transport placards under an entirely separate regime, so a single truck can carry two hazard systems using one geometry to mean two different things.
Cultural flips: The standard overrides local colour reading by design, as ISO 7010 does (→ VG·0003), and inherits the same bet: that a taught grammar beats an intuited one. Where it differs is that the audience is occupational rather than general, so the training the grammar assumes actually exists — which may be the reason it works better than laundry care, whose grammar is arguably cleaner.

Sources · 3

documented The Globally Harmonized System of Classification and Labelling of Chemicals (the UN “purple book”), and the nine pictograms.
documented EU CLP Regulation and US OSHA HazCom as the implementing instruments.
traditional The criticism of the exclamation-mark and health-hazard pictograms. Comprehension studies exist and are mixed; the Institute is stating a judgement, not a measured result.