Under the HSNO Act, a hazardous substance is any substance that has one or more hazardous property, above specified levels. Hazardous substances can have more than one hazardous property.  

We use the Globally Harmonised System (GHS 7) hazard classification system in New Zealand. Hazard classifications are communicated on labels and safety data sheets including the safe way to store, use and dispose of chemicals.

The GHS 7 assigns classifications to a hazardous substance based on its:

• physical hazards (such as flammability)
• human health hazards (such as acute toxicity)
• environmental hazards (such as whether it is hazardous to the aquatic environment). 

A hazard classification comes in two parts:

1. the hazard class – this refers to the nature of the hazard the substance poses, and are grouped into physical, health or environmental hazards
2. the hazard category – this refers to hazard severity within a hazard class; the lower the category number the more severe the hazard.

For example:

• Acute oral toxicity Category 1: acute oral toxicity is the hazard class, Category 1 is the category.
• A substance with the hazard classification acute oral toxicity Category 1 is more toxic than a substance with the hazard classification acute oral toxicity Category 4.

Some of the hazard classes have sub categories, types, divisions or groups as well as or instead of categories. These can differ based on severity, how the substance is packaged or on various physical properties. Below is the list of hazard classification and their correlation to the previous HSNO classification system used. This document is also available as a PDF:

HSNO to GHS7 Correlation table (PDF, 241KB)