Glossary / Documents & labels
Hazard class
A hazard class is the nature of a physical, health, or environmental hazard in the GHS classification system, such as flammable liquids, acute toxicity, or skin corrosion. Each class is subdivided into categories that show how severe the hazard is.
Explanation
GHS organizes hazards into three groups: physical hazards, health hazards, and environmental hazards. Within each group are many classes. Physical hazard classes include explosives, flammable gases, and oxidizing liquids. Health hazard classes include acute toxicity, skin corrosion and irritation, serious eye damage, sensitization, and carcinogenicity.
A class describes the type of danger, while the hazard category describes its degree. A flammable liquid is the class; Category 1, 2, 3, or 4 tells you how severe it is. Some classes also use types or divisions instead of categories.
The classification drives the label. Once a product is placed in a class and category, the signal word, pictogram, and hazard statement follow from the criteria. Because every supplier uses the same criteria, labels for similar hazards look alike.
Not every country adopts every class. OSHA's HazCom omits the environmental classes, and a few classes in other systems have no US equivalent. Meanwhile, hazards not covered by any class may fall under HNOC.
Do not confuse GHS classes with the DOT hazard classes used for shipping, which are numbered one through nine and follow a separate system.
What to do and watch for
- Look at the hazard class first to understand the type of danger.
- Use the category to judge relative severity within the class.
- Keep GHS classes distinct from transport classes in training.
Where it appears on an SDS
- Section 2: Hazard identification. The classification of the product, listing each hazard class and category assigned, is the first item in the hazard identification section.
SDS content and wording vary by supplier. This page is general reference and does not replace the current SDS for your product.
Related terms
- Hazard category
- Globally Harmonized System (GHS)
- Pictogram
- Hazard statement
- DOT hazard class
- Hazard not otherwise classified (HNOC)