Signal Word

The Signal Word is the single word on a chemical label that indicates the relative severity of the hazard under the UN Globally Harmonized System. Two signal words are defined: “Danger” for the most severe hazard categories, “Warning” for less severe categories. Some hazard categories require no signal word, typically the lowest-severity Category 5 entries that exist for a few hazard classes. The signal word appears in bold uppercase below the pictograms on the label, and the language is translated for each destination market (“Gefahr” / “Achtung” in German, “Danger” / “Attention” in French, etc.).

Which signal word applies

The signal word is determined by the highest-severity hazard classification on the substance. If any one of the substance’s hazards triggers “Danger”, the entire label uses “Danger”, regardless of how many other hazards trigger only “Warning”. The hierarchy is severity-based.

Categories typically triggering “Danger”:

• Acute toxicity Category 1, 2, or 3
• Skin corrosion Category 1
• Eye damage Category 1
• Carcinogenicity Category 1A or 1B
• Mutagenicity Category 1A or 1B
• Reproductive toxicity Category 1A or 1B
• Specific target organ toxicity Category 1
• Aspiration hazard Category 1
• Flammable liquids Category 1 or 2
• Self-reactive substances Type B
• Organic peroxides Type B
• Pyrophoric substances
• Self-heating Category 1
• Water-reactive Category 1
• Oxidising substances Category 1

Categories typically triggering “Warning”:

• Acute toxicity Category 4
• Skin irritation Category 2
• Eye irritation Category 2A
• Skin sensitisation Category 1
• Carcinogenicity Category 2 (suspected)
• Mutagenicity Category 2 (suspected)
• Reproductive toxicity Category 2 (suspected)
• Specific target organ toxicity Category 2
• Flammable liquids Category 3
• Self-heating Category 2
• Water-reactive Category 2 or 3
• Oxidising substances Category 2 or 3

Some Category 5 entries (in the few hazard classes that include Category 5) may have no signal word, the hazard is considered minor enough that the signal-word framing is not warranted.

How the signal word interacts with the rest of the label

The signal word is the third element a label-reader sees, after the pictogram and the product identifier. The reader’s mental model:

1. Pictogram → “what kind of hazard” (flame? skull? corrosion?)
2. Signal word → “how severe” (Danger or Warning)
3. H-statement → “what specifically does it do”
4. P-statement → “what should you do about it”

A “Danger” signal word with a flame pictogram indicates a Category 1 or 2 flammable. A “Warning” signal word with the same pictogram indicates a Category 3. The pictogram alone does not communicate severity; the signal word does.

Translations across jurisdictions

The official translations are published in each jurisdiction’s GHS implementation. EU translations are in CLP Annex II.

Signal word vs no-signal-word

Substances classified only in lower-severity categories (Category 5 for relevant hazards) have no signal word on the label. This is rare in commercial chemicals, most industrial substances classify into higher categories that trigger at least “Warning”.

If a label shows hazard pictograms but no signal word, the substance is classified only in categories that GHS does not require a signal word for. This is correct, not an omission. Verify by cross-referencing the substance’s full classification.

Verifying the signal word on Chinese factory labels

Two checks:

1. The signal word matches the hazard categories declared. A substance with H225 (Category 2 flammable liquid, Danger threshold) and H319 (Category 2A eye irritation, Warning threshold) should carry “Danger” on the label. H225 is the higher-severity hazard.
2. The translation matches the destination market. Chinese-only “危险” does not pass for US OSHA; needs “Danger” added.

The mismatch failure mode: a Chinese factory’s auto-generated label uses “Warning” for a substance that should carry “Danger” because the highest-severity hazard category was missed in the classification. Cross-check the H-statements against the GHS severity table to confirm.

Operator note: the dual-signal-word problem

Some legacy labels show both “Danger” and “Warning” on the same label, attached to different hazard groups. This is non-compliant under GHS. The label uses one signal word, the higher of the two. A label still showing the dual format is using a pre-GHS hazard communication style that should have been retired around 2015. Reject the label and request a current GHS-compliant version.

Related terms

GHS is the umbrella framework. GHS pictograms accompany the signal word. Hazard statement (H-codes) describes the hazard. Precautionary statement (P-codes) describes the recommended action. SDS section 2 carries the signal word for the substance.