Hazard class

The nature of a chemical hazard under GHS: flammable liquid, skin corrosion, carcinogenicity and so on.

A hazard class describes the kind of hazard a substance presents. GHS defines physical classes such as flammable liquid and oxidising solid, health classes such as acute toxicity and carcinogenicity, and environmental classes such as aquatic toxicity.

Within a class, a category gives the degree of severity, with category 1 generally the most severe. The class and category together determine the signal word, pictogram and hazard statement.

Tier II reporting groups chemicals by hazard category, which is derived from the GHS classification on the sheet.

Related terms

• GHSThe UN system that standardises how chemical hazards are classified, labelled and described on safety data sheets.
• SDS Section 2Hazard identification: the GHS classification, signal word, hazard statements and pictograms.
• Signal wordEither Danger or Warning, the GHS indicator of relative hazard severity.
• GHS pictogramOne of nine standard symbols in a red diamond indicating a category of chemical hazard.

A plain-English explanation, not legal advice. Figures are the federal baseline; your state may differ, so see the state-by-state requirements.