Globally Harmonized System (GHS)

The Globally Harmonized System (GHS) of Classification and Labelling of Chemicals is a United Nations framework that standardizes how chemical hazards are classified and communicated. It sets common criteria for physical and health hazards, standard label elements such as pictograms and signal words, and a 16-section Safety Data Sheet format used worldwide.

In the United States, the GHS is not a law on its own. It reaches employers through OSHA's Hazard Communication Standard, which adopted GHS elements in 2012 and updated them again in 2024.

What Is the Globally Harmonized System (GHS)?

Before the GHS, countries and agencies used different rules for deciding whether a chemical was hazardous and how to label it. The same product could carry several different labels and data sheets depending on where it was sold. The GHS, developed under the United Nations and first published in 2003, gives regulators a common set of building blocks. The UN publishes it in a document often called the "Purple Book" and revises it periodically.

Each country chooses which parts to adopt. In the US, OSHA's hazard communication standard, 29 CFR 1910.1200, aligned with GHS Revision 3 in a final rule published in March 2012. OSHA states on its Hazard Communication page that the standard is now aligned with the GHS, giving a common approach to classifying chemicals and communicating hazards on labels and safety data sheets.

On May 20, 2024, OSHA published a further update that primarily adopts elements of GHS Revision 7. It took effect on July 19, 2024. In January 2026, OSHA extended the compliance dates for that rule by four months.

Key Elements of the GHS

Hazard classification

The GHS sorts hazards into classes and categories:

• Physical hazards: for example explosives, flammable gases, liquids and solids, oxidizers, gases under pressure, self-reactive substances, pyrophorics and substances corrosive to metals.
• Health hazards: for example acute toxicity, skin corrosion or irritation, serious eye damage, respiratory or skin sensitization, germ cell mutagenicity, carcinogenicity, reproductive toxicity, specific target organ toxicity and aspiration hazard.
• Environmental hazards: aquatic toxicity and hazards to the ozone layer. OSHA did not adopt these, because environmental hazards fall outside its authority.

Within most classes, hazards are ranked by category, and category 1 is the most severe.

Label elements

Under the OSHA standard, labels on shipped containers must include:

• Product identifier
• Signal word: "Danger" for more severe hazards or "Warning" for less severe ones
• Hazard statements, such as "Highly flammable liquid and vapor"
• Pictograms
• Precautionary statements describing how to prevent, respond to, store and dispose of the chemical
• Name, address and telephone number of the chemical manufacturer, importer or other responsible party

Pictograms

GHS pictograms are black symbols on a white background inside a red diamond-shaped border. The GHS defines nine. OSHA requires eight of them; the environment pictogram is not mandatory under the Hazard Communication Standard. OSHA's pictogram QuickCard summarizes them:

• Health hazard: carcinogens, mutagens, reproductive toxicity, respiratory sensitizers, target organ toxicity and aspiration toxicity.
• Flame: flammables, pyrophorics, self-heating substances, substances that emit flammable gas, self-reactives and organic peroxides.
• Exclamation mark: irritants, skin sensitizers, acute toxicity (less severe), narcotic effects and respiratory tract irritation.
• Gas cylinder: gases under pressure.
• Corrosion: skin corrosion or burns, eye damage and corrosive to metals.
• Exploding bomb: explosives, self-reactives and organic peroxides.
• Flame over circle: oxidizers.
• Skull and crossbones: acute toxicity (fatal or toxic).

Safety Data Sheets

The GHS replaced varied material safety data sheet formats with a standard 16-section Safety Data Sheet (SDS). Sections 1 to 8 cover identification, hazards, composition, first aid, firefighting, accidental release, handling and storage, and exposure controls and personal protective equipment. Sections 9 to 11 cover physical and chemical properties, stability and reactivity, and toxicology. Sections 12 to 15 cover ecological, disposal, transport and regulatory information, and section 16 covers other information, including the date of preparation or last revision. OSHA does not enforce the content of sections 12 to 15 because those topics fall under other agencies, but the sections must be included.

The 2024 HCS Update and Compliance Dates

The 2024 final rule changed several details of how OSHA applies the GHS, including hazard classification criteria, new or revised physical hazard classes such as aerosols, desensitized explosives and chemicals under pressure, label provisions for small containers, SDS content, and how trade secret concentrations may be shown. Under the four-month extension OSHA published in January 2026, the compliance dates are:

• Substances, manufacturers, importers and distributors: May 19, 2026.
• Substances, employers (workplace labels, written program and training): November 20, 2026.
• Mixtures, manufacturers, importers and distributors: November 19, 2027.
• Mixtures, employers: May 19, 2028.

Until the applicable date, covered parties may comply with the 2012 standard, the 2024 standard or both. That means employees may see labels and SDSs in both formats for a while, so training should prepare them to recognize either version.

GHS vs. NFPA 704 and HMIS

Many workplaces also see NFPA 704 diamonds on buildings and tanks, and some use the HMIS rating system on in-house labels. These systems differ from the GHS in an important way:

• GHS: category 1 is the most severe hazard.
• NFPA 704 and HMIS: numbers run from 0 to 4, and 4 is the most severe.

A worker who sees a "1" can draw the opposite conclusion depending on the system. NFPA 704 is designed mainly for emergency responders, not for day-to-day handling. Employers can use NFPA or HMIS on workplace labels as long as employees still have immediate access to the specific hazard information required by the standard and are trained on the system used. Note also that DOT transport labels follow the UN Model Regulations and look different from GHS workplace labels.

How to Implement GHS in Your Workplace

1. Inventory your chemicals. List every hazardous chemical on site, by location.
2. Collect current SDSs. Make sure each product has a GHS-format SDS from the supplier and replace outdated versions as updated SDSs arrive.
3. Review labels. Check incoming containers for compliant labels and set rules for labeling secondary containers in the workplace.
4. Update your written program. Your hazard communication program should describe labeling, SDS access and training.
5. Train employees. Teach workers how to read GHS labels and SDSs, what each pictogram means, and how category numbers differ from NFPA ratings.
6. Keep SDSs accessible. Employees must be able to get SDSs readily during each work shift, whether on paper or electronically.

Common Mistakes to Avoid

• Unlabeled secondary containers. Spray bottles and transfer containers often end up with no label at all.
• Outdated SDS binders. Old MSDSs or superseded SDSs can give workers the wrong information.
• Confusing rating systems. Training that does not explain the GHS category scale can leave workers misreading hazards.
• Missing the employer deadlines. Updated supplier labels and SDSs mean employers need to refresh workplace labels and training by their own compliance dates.

How SMS360 Helps

SMS360 Safety Data Sheets helps you keep a central, searchable library of SDSs for the chemicals at each site. Employees can look up the current SDS from a desktop or mobile device, and administrators can track which sheets need updating as suppliers issue revised versions. Keeping records in one place supports your hazard communication program and makes it easier to show that workers have access to GHS-format information during every shift.

Frequently Asked Questions

Is GHS mandatory in the United States?

The GHS itself is a UN framework, not a US law. However, OSHA's Hazard Communication Standard, 29 CFR 1910.1200, incorporates GHS classification criteria, label elements and the 16-section SDS format, so chemical manufacturers, importers, distributors and employers covered by the standard must follow those GHS-based requirements.

How many GHS pictograms are there?

The GHS defines nine pictograms. OSHA requires eight of them on labels under the Hazard Communication Standard: health hazard, flame, exclamation mark, gas cylinder, corrosion, exploding bomb, flame over circle, and skull and crossbones. The ninth, the environment pictogram, is not mandatory under OSHA rules but may appear on labels.

What does a GHS label need to include?

Labels on shipped containers must show a product identifier, a signal word, hazard statements, pictograms, precautionary statements, and the name, address and phone number of the responsible manufacturer, importer or distributor. Workplace secondary containers can use other effective labeling methods if employees still get the required hazard information.

When must employers comply with the 2024 GHS update?

Under the January 2026 extension, employers must update workplace labeling, hazard communication programs and training for substances by November 20, 2026, and for mixtures by May 19, 2028. Manufacturers, importers and distributors face earlier dates: May 19, 2026, for substances and November 19, 2027, for mixtures.