The rule
- Danger is reserved for the most severe hazard categories (typically Cat. 1 and 2).
- Warning covers less severe categories (typically Cat. 3 to 5).
- If a product qualifies for both, only Danger appears on the label.
- Products classified only in the lowest categories (e.g. some aquatic Cat. 4) carry no signal word.
Examples
- Concentrated sulfuric acid: Skin corrosion Cat. 1A → Danger.
- Diluted acetic acid (vinegar-strength): Skin irritation Cat. 2 → Warning.
- Sodium hydroxide 50%: Skin corrosion Cat. 1A + acute inhalation → Danger.
Why it matters
Under OSHA HazCom 2012 and EU CLP, the signal word is what a worker sees first in an emergency. Getting it right (or wrong) is what regulators check first during a labelling audit.