Find out what hazardous substances are and why they must be managed safely.

What is a hazardous substance?

The term hazardous substance refers to any product or chemical that has properties that are explosive, flammable, oxidising, toxic, corrosive or toxic to the environment.

  • Explosive – explodes or causes explosion.
  • Flammable – ignites easily and burns rapidly.
  • Oxidising – could be gaseous, solid or liquid and can cause or intensify fire and explosion.
  • Toxic – can harm people if it enters the body through contact, being inhaled or ingested. The effects can range from mild to life threatening, and can be immediate or long term.
  • Corrosive – can cause severe skin burns and eye damage.
  • Ecotoxic – is toxic to the environment.

The definition of ‘substance’ is provided in Section 2 of the Hazardous Substances and New Organisms Act 1996(external link).

Hazardous substances are an integral part of modern society. They are found across a wide range of industries, including:

  • agrichemicals used in primary production
  • fuels that run our transport fleet
  • explosives for mining and quarrying
  • solvents and other general chemicals used in manufacturing
  • cleaning solutions that are critical for safe food production, and
  • speciality chemicals that underpin research and development.

By their very nature hazardous substances can be extremely dangerous. Used safely they contribute to New Zealand’s economic growth and prosperity. Used incorrectly they can cause catastrophic accidents, such as fires and explosions, and serious harm to people who are exposed to them.

Occupational exposure to hazardous substances may occur over many years and result in slow and debilitating diseases, many of which are fatal. Around 600 – 900 people die prematurely every year from workplace-related disease including from exposure to hazardous substances.


All hazardous substances are required to have an approval under the Hazardous Substances and New Organisms (HSNO) Act.

The Environmental Protection Authority (EPA) is responsible for approving hazardous substances for use in New Zealand. This includes substances that are imported into New Zealand or manufactured here.  

When the EPA receives a new application for a hazardous substance approval, WorkSafe will make sure the rules will sufficiently protect the health and safety of people from work-related activities involving the substance.

For more information about the hazardous substances application process see the HSNO reform page of the EPA website(external link).


The hazardous properties of a substance are classified to determine how the risks can be managed. There are eight key hazard classes:

  • Class 1: explosives
  • Class 2: flammable gases
  • Class 3: flammable liquids
  • Class 4: flammable solids
  • Class 5: oxidising substances
  • Class 6: substances toxic to people
  • Class 8: corrosive substances
  • Class 9: substances toxic to the environment

(Class 7 is missing as it covers radioactive materials which are regulated under the Radiation Safety Act 2016.)

Approved hazardous substances with controls

The EPA website has a database(external link) containing information on the classifications and controls for all approved hazardous substances.

Refer to the EPA website(external link) for more information on hazardous substances.