Chemical Hazard Labels and GHS Pictograms
The Globally Harmonized System (GHS) is an international system for classifying and labeling chemicals, and it uses nine pictograms, signal words (Danger or Warning), hazard statements and precautionary statements to communicate hazards. In brief: a red-bordered diamond with a flame means flammable, a skull and crossbones means acute toxicity, and a diamond with a corroding hand and surface means corrosive; always read the signal word and hazard statements on the label.
Labels are the first line of information about a chemical. A user who can read them correctly knows what the main hazards are, what protection to wear and how to react to an accident. This article explains the elements of a GHS label, describes each of the nine pictograms in a table, explains hazard and precautionary statements, introduces safety data sheets, works through reading a real-style label and gives the history of the GHS.
What appears on a GHS label?
- Product identifier: the chemical name or product name.
- Pictograms: symbols in a red-bordered diamond that show the type of hazard.
- Signal word: Danger for the more severe hazards and Warning for the less severe.
- Hazard statements: standard phrases that describe the nature of the hazard, for example “Highly flammable liquid and vapour”.
- Precautionary statements: advice on prevention, response, storage and disposal.
- Supplier information: the name, address and telephone number of the manufacturer or distributor.
What do the nine GHS pictograms mean?
| Code | Symbol | Main hazards | Example |
|---|---|---|---|
| GHS01 | Exploding bomb | Explosives, some organic peroxides | Nitroglycerin |
| GHS02 | Flame | Flammable gases, liquids and solids; some water-reactive substances | Ethanol, acetone, sodium metal |
| GHS03 | Flame over circle | Oxidizers that can start or intensify fires | Potassium nitrate, hydrogen peroxide (high concentration) |
| GHS04 | Gas cylinder | Gases under pressure | Compressed nitrogen |
| GHS05 | Corrosion | Corrosive to skin, eyes and metals | Sulfuric acid, sodium hydroxide |
| GHS06 | Skull and crossbones | Acute toxicity, fatal or toxic | Cyanide salts, methanol (toxic) |
| GHS07 | Exclamation mark | Irritant, skin sensitizer, harmful, narcotic effects | Dilute acids, many solvents |
| GHS08 | Health hazard | Carcinogen, mutagen, reproductive toxicity, respiratory sensitizer, organ damage | Benzene, asbestos |
| GHS09 | Environment | Harmful to aquatic life | Some pesticides, copper salts |
Not all pictograms appear on every label, and a chemical may carry several.
What are hazard and precautionary statements?
Hazard statements are coded with an H and three digits. H2xx statements describe physical hazards, H3xx describe health hazards and H4xx describe environmental hazards. Precautionary statements are coded with a P and three digits, where P1xx is general, P2xx is prevention, P3xx is response, P4xx is storage and P5xx is disposal.
| Code | Text | Type |
|---|---|---|
| H225 | Highly flammable liquid and vapor | Hazard (physical) |
| H290 | May be corrosive to metals | Hazard (physical) |
| H302 | Harmful if swallowed | Hazard (health) |
| H314 | Causes severe skin burns and eye damage | Hazard (health) |
| H410 | Very toxic to aquatic life with long lasting effects | Hazard (environment) |
| P210 | Keep away from heat, sparks, open flames and hot surfaces. No smoking | Prevention |
| P280 | Wear protective gloves, protective clothing and eye protection | Prevention |
| P305+P351+P338 | If in eyes: rinse cautiously with water for several minutes; remove contact lenses if present and easy to do; continue rinsing | Response |
What is a safety data sheet?
A safety data sheet (SDS) is a document of 16 standard sections that gives detailed information on a chemical. It includes the identification of the product, hazards, composition, first-aid measures, firefighting measures, accidental release measures, handling and storage, exposure controls and personal protection, physical and chemical properties, stability and reactivity, toxicological information, ecological information, disposal, transport, regulatory information and other data. Suppliers must provide an SDS, and workplaces must keep it accessible.
What other labeling systems exist?
The NFPA 704 diamond is used on buildings and storage areas to inform emergency responders. It has four colored sections: blue for health, red for flammability, yellow for instability or reactivity and white for special hazards, and each of the first three has a rating from 0 (minimal) to 4 (severe). Transport labels, which follow United Nations rules, show hazard classes on containers during shipment. Some older labels still use orange squares of the previous European system, and a lab may have bottles with both kinds of labels.
Worked example: reading a label
A bottle of concentrated hydrochloric acid has the following information: GHS05 (corrosion) and GHS07 (exclamation mark), signal word Danger, hazard statements H290, H314 and H335, and precautionary statements including P260, P280 and P303+P361+P353.
- Hazard class. GHS05 means it is corrosive. The signal word Danger confirms a serious hazard.
- H290: may be corrosive to metals, so do not store it in a metal cabinet or use metal tools.
- H314: causes severe skin burns and eye damage, so goggles, gloves and a lab coat are essential.
- H335: may cause respiratory irritation, so work in a fume hood, because the acid releases fumes.
- P303+P361+P353: if on skin (or hair), take off immediately all contaminated clothing and rinse skin with water or shower.
- Conclusion. Wear goggles, nitrile gloves and a lab coat, work in a fume hood, keep the bottle away from metals and know where the eyewash is located.
How did the GHS develop?
Before the GHS, countries had different systems, so the same chemical could carry different labels in different countries. The idea of a worldwide system came from the 1992 United Nations Conference on Environment and Development in Rio de Janeiro. The first edition of the GHS, called the “Purple Book”, was published in 2003 by the United Nations, and it is revised every two years. Countries adopt it at different times and with some local variations, so details such as the exact wording or the categories used can differ.
Which mistakes are common?
Mistake 1: Ignoring the signal word
Danger indicates more severe hazards than Warning, and it should change how carefully you work.
Mistake 2: Thinking that no pictogram means no hazard
Some chemicals have hazards that are not covered by pictograms, and unlabeled bottles must be treated as unknown and dangerous.
Mistake 3: Confusing the exclamation mark with a minor hazard
It signals irritation and harm, and these can still cause injury. Follow the precautionary statements.
Mistake 4: Relying only on the label
The label is a summary. The safety data sheet has full information, especially about first aid and spills.