Classifications of Hazardous Substances

The following is the breakdown of the HSNO classification system which is based on the Globally Harmonized System (GHS).

If you need further information on classifications and the thresholds which apply see the User Guide HSNO Thresholds & Classifications - summary.

Explosives - Class 1

The explosive property classification scheme groups explosive substances in terms of three effects:

  • their degree of sensitiveness to stimuli
  • their different types of explosive effect
  • the different levels at which those explosive effects may be displayed.

The classification for substances with an explosive property is based on:

  • subclasses (divisions) for types and levels of explosiveness and for sensitiveness of the substance to stimuli
  • categories (compatibility groupings) for explosive type.

Classification requires allocation of a subclass and a category. A substance or article is classified as being in a particular subclass or category if it meets certain criteria:

The subclasses (divisions) for types and levels of explosive effect and for sensitiveness of the substance to stimuli are:

Subclass 1.1
Substances and articles that have a 'Mass Explosion Hazard'
Subclass 1.2
Substances and articles that have a 'Projection Hazard' but not a mass explosion hazard
Subclass 1.3
Substances and articles that have a 'Fire Hazard' and either a minor blast hazard or a minor projection hazard, or both, but not a mass explosion hazard
Subclass 1.4
Substances and articles that present 'No Significant Hazard', but a minor fire or projection hazard
Subclass 1.5
'Very Insensitive' substances that have a 'Mass Explosion Hazard'
Subclass 1.6
'Extremely Insensitive' articles which do not have a 'Mass Explosion Hazard'

The classification categories (compatibility groupings) for explosive type and properties , are as follows:

Category A
Primary explosive substances, ie very sensitive to heat, impact or friction or able to transmit detonation or deflagration to secondary explosive substances close to it.
Category B
Articles designed to be primers, detonators and detonator assemblies for blasting usually containing a primary explosive substance but not containing two or more effective protective features.
Category C
Propellant explosive substances (deflagrating explosive used for propulsion) or other deflagrating explosive substances, and articles containing such explosive substances.
Category D
Secondary detonating explosive substances, ie less sensitive than primary detonating substances and more sensitive than substances falling into Category N €‘ or black powder, or articles containing such secondary detonating explosive substances, in each case without means of initiation and without a propelling charge; and articles containing a primary explosive substance and two or more effective protective features.
Category E
Articles containing a secondary detonating explosive substance, without means of initiation, but with a propelling charge (other than one containing a flammable liquid or gel or hypergolic liquids which ignite spontaneously on contact with an oxidant).
Category F
Articles containing a secondary detonating explosive substance with its own means of initiation, without a propelling charge or with a propelling charge (other than one containing a flammable liquid or gel or hypergolic liquids).
Category G
Pyrotechnic substances, or articles containing a pyrotechnic substance, or articles containing both an explosive substance and an illuminating, incendiary, tear- or smoke- producing substance (other than a water-activated article or one containing white phosphorus, phosphides, a pyrophoric substance, a flammable liquid or gel, or hypergolic liquids).
Category H
Articles containing both an explosive substance and white phosphorus (for smoke generation but represents a fire hazard from spontaneous ignition on contact with air).
Category J
Articles containing both an explosive substance and a flammable liquid or gel.
Category K
Articles containing both an explosive substance and a substance with an acute toxicity of HSNO classification 6.1A, 6.1B or 6.1C.
Category L
A mixture or an article that contains both an explosive substance and a substance that spontaneously combusts, detonates or deflagrates if exposed to air, water, oxidising substances or flammable substances, or generates a substance that spontaneously combusts, detonates or deflagrates when exposed to air or water.
Category N
Articles containing only extremely insensitive detonating substances where extremely insensitive is as defined in the criteria for Subclass 1.6 above.
Category S
Substances or articles where hazardous effects arising from their accidental functioning are confined within the package, or, where the package is degraded by fire, any blast or projection effects are so limited they would not be capable of causing bodily harm within 5 m of the articles, or any blast or projection effects are largely confined to the package.

Flammables - Classes 2, 3 and 4

Under the HSNO Act classification system for flammability, there are separate thresholds and classifications for substances in gas, liquid and solid form, with solid substances being further subdivided into different types of flammable property.

Overall, there are nine subclasses to the classification system for flammable substances, with corresponding threshold levels. Briefly these are:

  • ignitibility for flammable gases (subclass 2.1.1)
  • flammable components for flammable aerosols (subclass 2.1.2)
  • ignitibility for flammable liquids (subclass 3.1)
  • liquid desensitised explosives (subclass 3.2)
  • flammable solids, divided into:
    1. i) flammable solids (readily combustible solids and solids which may cause fire through friction) (subclass 4.1.1)
    2. ii) self-reactive substances (subclass 4.1.2)
    3. iii) solid desensitised explosives (subclass 4.1.3)
    4. iv) substances liable to spontaneous combustion, pyrophoric and self heating substances (subclass 4.2)
    5. v) substances which in contact with water emit flammable gases (subclass 4.3).

(It should be noted that substances classified as class 4 flammable solids are not necessarily solids)

Oxidisers - Classes 5

There are 2 parts to the threshold for substances with an oxidising property:

oxidising substances not organic peroxides
being substances which, while in themselves not necessarily combustible, may cause or contribute to the combustion of other substances or material
organic peroxides
being substances which contain the bivalent oxygen [-0-0-] structure and may be considered as derivatives of hydrogen peroxide where one or both of the hydrogen atoms has been replaced by an organic radical.

Oxidising substances are divided into subclass as follows:

  • 5.1.1 - solids and liquids
  • 5.1.2 - gases
  • 5.2 - organic peroxides

Each subclass is divided into several categories representing different degrees of hazard, except in the case of subclass 5.1.2 where there is only one category (A being the highest degree of hazard).

Toxics - Class 6

There are a number of subclasses under the toxic property as follows:

  • Subclass 6.1 - Substances which are acutely toxic
  • Subclass 6.3 - Substances which are skin irritants
  • Subclass 6.4 - Substances which are eye irritants
  • Subclass 6.5 - Substances which are sensitisers
  • Subclass 6.6 - Substances which are mutagenic
  • Subclass 6.7 - Substances which are carcinogenic
  • Subclass 6.8 - Substances which are reproductive or developmental toxicants
  • Subclass 6.9 - Substances which are target organ systemic toxicants.

Note that Class 6.2 is omitted from the above list as the numbering system used in the Regulations reflects the UNRTDG numbering system. Under the UNRTDG system, Class 6.2 is assigned to infectious substances which are not cover by HSNO.

Radioactive - Class 7

Radioactive substances are not included in HSNO. Refer to the National Radiation Laboratory

Corrosives - Classes 8

The HSNO legislation defines 3 sub-classes under the corrosive property as follows:

  • Subclass 8.1 - Substances corrosive to metals
  • Subclass 8.2 - Substances corrosive to dermal tissue
  • Subclass 8.3 - Substances corrosive to ocular tissue

There are also 3 degrees of hazard defined by specific thresholds - A, B and C (A being the highest degree of hazard).

Ecotoxic - Classes 9

There are four subclasses under the ecotoxic property as follows:

  • Aquatic effects (Subclass 9.1)
  • Soil effects (Subclass 9.2)
  • Terrestrial vertebrate effects (Subclass 9.3)
  • Terrestrial invertebrate effects (Subclass 9.4)

There is also a threshold set for a substance that is used as a biocide. Any substance that triggers this effect is subsequently classified within the appropriate sub-class of ecotoxic effects above.

Within each subclass, there are degrees of hazard defined by specific thresholds - A, B, C and D (A being the highest degree of hazard).