Hazard pictograms form part of the international Globally Harmonized System of Classification and Labelling of Chemicals (GHS). Two sets of pictograms are included within the GHS: one for the labelling of containers and for workplace hazard warnings, and a second for use during the transport of dangerous goods. Either one or the other is chosen, depending on the target audience, but the two are not used together. The two sets of pictograms use the same symbols for the same hazards, although certain symbols are not required for transport pictograms. Transport pictograms come in wider variety of colors and may contain additional information such as a subcategory number.
Hazard pictograms are one of the key elements for the labelling of containers under the GHS, along with:
an identification of the product;
a signal word – either Danger or Warning – where necessary
hazard statements, indicating the nature and degree of the risks posed by the product
precautionary statements, indicating how the product should be handled to minimize risks to the user (as well as to other people and the general environment)
the identity of the supplier (who might be a manufacturer or importer)
The GHS chemical hazard pictograms are intended to provide the basis for or to replace national systems of hazard pictograms. It has still to be implemented by the European Union (CLP regulation) in 2009.
Flammable gases – Gases which at 20 °C and a standard pressure of 101.3 kPa:
are ignitable when in a mixture of 13 percent or less by volume with air; or
have a flammable range with air of at least 12 percentage points regardless of the lower flammable limit.
Non-flammable non-toxic gases – Gases which:
are asphyxiant – gases which dilute or replace the oxygen normally in the atmosphere; or
are oxidizing – gases which may, generally by providing oxygen, cause or contribute to the combustion of other material more than air does; or
do not come under the other divisions.
Toxic gases – Gases which:
are known to be so toxic or corrosive to humans as to pose a hazard to health; or
are presumed to be toxic or corrosive to humans because they have an LC50 value equal to or less than 5000 ml/m3 (ppm).
e.g. hydrogen cyanide
Classes 3 and 4: Flammable liquids and solids
Flammable liquids – Liquids which have a flash point of less than 60 °C and which are capable of sustaining combustion
Flammable solids, self-reactive substances and solid desensitized explosives – Solids which, under conditions encountered in transport, are readily combustible or may cause or contribute to fire through friction; self-reactive substances which are liable to undergo a strongly exothermic reaction; solid desensitized explosives which may explode if not diluted sufficiently
Substances liable to spontaneous combustion – Substances which are liable to spontaneous heating under normal conditions encountered in transport, or to heating up in contact with air, and being then liable to catch fire
e.g. manganese heptoxide
Substances which in contact with water emit flammable gases – Substances which, by interaction with water, are liable to become spontaneously flammable or to give off flammable gases in dangerous quantities
Oxidizing substances – Substances which, while in themselves not necessarily combustible, may, generally by yielding oxygen, cause, or contribute to, the combustion of other material
Organic peroxides – Organic substances which contain the bivalent –O–O– structure and may be considered derivatives of hydrogen peroxide, where one or both of the hydrogen atoms have been replaced by organic radicals
Toxic substances – Substances with an LD50 value ≤ 300 mg/kg (oral) or ≤ 1000 mg/kg (dermal) or an LC50 value ≤ 4000 ml/m3 (inhalation of dusts or mists)
e.g. nearly everything that contains cyanide groups
Corrosive substances – Substances which:
cause full thickness destruction of intact skin tissue on exposure time of less than 4 hours; or
exhibit a corrosion rate of more than 6.25 mm per year on either steel or aluminium surfaces at 55 °C