GHS stands for the Globally Harmonized System of Classification and Labelling of Chemicals. It’s an international framework developed by the United Nations that standardizes how chemicals are classified by hazard type and how that information appears on labels and safety documents. Before GHS, different countries used entirely different symbols, warning words, and safety sheets for the same chemical, creating confusion for workers, emergency responders, and companies shipping products across borders. GHS replaced that patchwork with one universal system now adopted by dozens of countries.
How GHS Classifies Chemical Hazards
GHS sorts every chemical hazard into one of three broad groups: physical hazards, health hazards, and environmental hazards. Within those groups, there are 28 specific hazard classes.
Physical hazards cover 16 classes, including explosives, flammable gases, flammable liquids, flammable solids, oxidizing gases, gases under pressure, substances that self-heat, and chemicals that are corrosive to metals. These describe what a chemical can do on its own or when it contacts other materials.
Health hazards cover 10 classes that describe what a chemical can do to your body. These range from acute toxicity (immediate poisoning from a single exposure) to longer-term dangers like carcinogenicity, reproductive toxicity, and organ damage from repeated exposure. Skin and eye irritation, respiratory sensitization, and aspiration toxicity (inhaling a chemical into your lungs) are also included.
Environmental hazards cover two classes, both related to toxicity in aquatic environments: one for immediate harm to aquatic life and one for long-term harm.
The Nine Pictograms
One of the most recognizable parts of GHS is its set of nine pictograms. These are diamond-shaped symbols with a red border, white background, and a black icon inside. Each one represents a specific type of hazard:
- Exploding bomb: explosives and self-reactive substances
- Flame: flammable gases, liquids, solids, and self-heating chemicals
- Flame over circle: oxidizers that can intensify a fire
- Gas cylinder: compressed, liquefied, or dissolved gases under pressure
- Corrosion: chemicals that cause skin burns, eye damage, or corrode metals
- Skull and crossbones: chemicals with severe acute toxicity (can be fatal or toxic in small amounts)
- Exclamation mark: lower-level irritants, skin sensitizers, or chemicals harmful in larger doses
- Health hazard (silhouette with a starburst on the chest): carcinogens, reproductive toxins, organ-damaging substances, and respiratory sensitizers
- Environment (dead tree and fish): chemicals toxic to aquatic life
Each pictogram can only appear once on a label, even if multiple hazards fall under the same symbol.
What Goes on a GHS Label
GHS labels contain several standardized elements beyond pictograms. Every label includes a product identifier, the supplier’s contact information, relevant pictograms, a signal word, hazard statements, and precautionary statements.
The signal word is either “Danger” or “Warning.” Danger indicates the more severe hazard level, while Warning is used for less severe categories. Only one signal word appears on a label.
Hazard statements describe the nature of the hazard in a short phrase, such as “Fatal if swallowed” or “Causes serious eye damage.” Precautionary statements tell you what to do to minimize risk or respond to exposure, covering prevention, response, storage, and disposal. These statements are standardized with code numbers (H-codes for hazards, P-codes for precautions) so they translate consistently across languages.
Safety Data Sheets
GHS also standardized Safety Data Sheets (commonly called SDSs, formerly known as MSDSs). Every SDS follows the same 16-section format worldwide. The first three sections cover identification, hazard classification, and chemical composition. Sections 4 through 6 address emergencies: first aid, firefighting measures, and spill cleanup. Sections 7 and 8 cover safe handling, storage, and the protective equipment workers should use.
The remaining sections provide technical and regulatory details, including physical and chemical properties (appearance, odor, flash point, pH), stability and reactivity data, toxicological information, ecological impact, disposal considerations, transport information, regulatory status, and other relevant data. This consistent structure means that whether you’re reading an SDS from Japan or Germany, the information you need is always in the same place.
GHS in the United States
In the U.S., GHS is implemented through OSHA’s Hazard Communication Standard (HCS), which applies to workplaces. OSHA published an updated final rule on May 20, 2024, aligning the standard primarily with Revision 7 of the GHS. That update took effect on July 19, 2024, and includes changes to health and physical hazard criteria, a new hazard class for desensitized explosives, revised labeling rules for small containers and bulk shipments, and updated SDS requirements.
The transition is happening on a staggered timeline. Chemical manufacturers and importers have 18 months from the effective date to update labels and SDSs for individual substances, and 36 months for mixtures. Employers then get an additional 6 months after each deadline to update their workplace labels and training programs. During the transition, companies can comply with either the old or new version of the standard.
One notable gap: the EPA has not adopted GHS for pesticide labeling, and consumer products in the U.S. are not currently covered by GHS requirements.
Global Adoption
GHS has been adopted in some form across most major economies. The European Union, including France, Germany, Italy, and the United Kingdom, implemented GHS for workplaces and other sectors starting in 2009. Australia completed its transition to GHS Revision 7 at the end of 2023. Japan, South Korea, China, Brazil, Mexico, Argentina, Indonesia, South Africa, and Singapore have all implemented GHS for workplace chemicals, though they may align with different revision numbers.
Canada published amendments aligning with GHS Revision 7 in January 2023, with a transition period ending in December 2025. The system is now in its 11th revision, published by the United Nations in 2025, though individual countries typically lag a few revisions behind as they update their domestic regulations.
Countries adopt GHS as a “building block” approach, meaning they can choose which hazard classes and categories to implement. This is why you may still see some variation between countries, particularly for environmental hazard classes, which are not mandatory in every jurisdiction. Despite these differences, the core framework of pictograms, signal words, hazard statements, and standardized SDSs remains consistent, making it far easier to handle chemicals safely across international borders than it was before GHS existed.