GHS Labels: Pictograms & Signal Words

Every container of hazardous chemicals in a lab, from a five-gallon drum of solvent to a small vial of reagent, is supposed to carry a label that tells you what’s inside and how it can hurt you, before you ever open it or reach for a Safety Data Sheet (SDS). That label follows a single international system: the Globally Harmonized System of Classification and Labelling of Chemicals, or GHS. This guide walks through every required element of a GHS label — the nine pictograms, the two signal words, hazard statements, precautionary statements, and the identifying information — so lab staff, EHS officers, and anyone receiving or shipping chemicals can read one correctly on sight.

What Is the GHS, and Why Does the Label Look the Way It Does?

Before GHS, countries and even individual industries used different, incompatible systems for classifying chemical hazards and labeling containers — a solvent could be labeled “flammable” one way for transport, another way for workplace safety, and a third way in a different country entirely. The United Nations developed the GHS to standardize hazard classification criteria and the label/Safety Data Sheet format worldwide, so a pictogram means the same thing whether a chemical is manufactured in Germany, shipped through Singapore, or used in a lab in Ohio.

In the United States, GHS is implemented through OSHA’s Hazard Communication Standard (HCS, 29 CFR 1910.1200). OSHA first aligned HCS with GHS in 2012 (“HazCom 2012” or “HCS 2012”). OSHA issued a further final rule on May 20, 2024, effective July 19, 2024, updating HCS to align primarily with GHS Revision 7 (with some concepts drawn from Revision 8), with a compliance deadline of January 19, 2026 for manufacturers and importers to update labels and SDSs to the revised criteria. Because the UN revises GHS roughly every two years and individual countries adopt revisions on their own timelines, a label’s exact wording can vary slightly by revision year even though the six core elements described below stay the same.

GHS applies to workplace container labels. It is distinct from — but closely related to — the 16-section Safety Data Sheet that must accompany every hazardous chemical; the label is the at-a-glance summary, the SDS is the full technical reference.

The Six Required Elements of a GHS Label

Under HCS 2012 (and carried forward in the 2024 update), every label on a hazardous chemical shipped or used in a workplace must include:

Product identifier — the chemical name, code number, or batch number that matches the identifier used on the corresponding SDS.
Signal word — either “Danger” or “Warning,” indicating relative severity (see below).
Hazard statement(s) — standardized phrases describing the nature and degree of each hazard.
Pictogram(s) — up to nine red-bordered diamond symbols indicating hazard classes.
Precautionary statement(s) — standardized phrases describing how to minimize or prevent harmful exposure, or actions to take if exposure occurs.
Supplier identification — the name, address, and telephone number of the chemical manufacturer, importer, or other responsible party.

The sections below cover pictograms, signal words, hazard statements, and precautionary statements in detail, since these are the elements people most often misread or misunderstand.

GHS Pictograms Explained

A GHS pictogram is a symbol printed in black on a white background, inside a diamond (square rotated 45 degrees) with a red border. There are nine standardized GHS pictograms in total. Eight are mandatory under OSHA’s HCS for workplace labels in the United States; the ninth (the environmental pictogram, described last) is not required by OSHA but does appear internationally and on some transport documentation. A container can carry more than one pictogram if it presents more than one hazard class.

Because images aren’t reproduced in this version of the guide, each entry below describes exactly what to look for on the physical symbol.

1. Health Hazard

Symbol: A human silhouette (chest/torso) with a burst or star shape (“exclamation”) over the chest area, representing internal damage.
Indicates: Carcinogenicity, respiratory sensitization, reproductive toxicity, target organ toxicity, mutagenicity (germ cell), and aspiration toxicity — i.e., chronic or serious internal health effects rather than immediate acute poisoning.
Example chemicals: Formaldehyde (carcinogen), many chlorinated solvents.

2. Flame

Symbol: A stylized flame.
Indicates: Flammable liquids, gases, aerosols, and solids; pyrophorics (ignite spontaneously in air); self-heating substances; substances that emit flammable gas on contact with water; self-reactive substances; and organic peroxides.
Example chemicals: Ethanol, acetone, diethyl ether.

3. Exclamation Mark

Symbol: A simple exclamation point (!).
Indicates: The “lower-severity” catch-all class — skin and eye irritation, skin sensitization, acute toxicity (harmful, but not the more severe skull-and-crossbones category), narcotic effects, respiratory tract irritation, and hazard to the ozone layer.
Example chemicals: Many common lab detergents and mild irritant solvents.

4. Gas Cylinder

Symbol: A gas cylinder/tank outline.
Indicates: Gases under pressure — compressed, liquefied, refrigerated liquefied, or dissolved gases.
Example chemicals: Compressed nitrogen, argon, carbon dioxide cylinders.

5. Corrosion

Symbol: Two test-tube-like shapes pouring liquid onto a hand and a flat surface, both shown being visibly eaten away.
Indicates: Skin corrosion/burns, serious eye damage, and corrosive effects on metals.
Example chemicals: Concentrated sulfuric acid, sodium hydroxide solution.

6. Exploding Bomb

Symbol: A black sphere with radiating fragments/explosion lines.
Indicates: Explosives, and self-reactive substances or organic peroxides that can detonate under certain conditions.
Example chemicals: Certain picric acid preparations, some aged ethers that have formed peroxides.

7. Flame Over Circle

Symbol: A flame symbol sitting directly above a circle.
Indicates: Oxidizers — substances that can cause or intensify fire in other materials, even though they aren’t themselves flammable.
Example chemicals: Hydrogen peroxide (concentrated), potassium permanganate.

8. Skull and Crossbones

Symbol: The classic skull-and-crossbones.
Indicates: Acute toxicity — the substance can be fatal or toxic if swallowed, absorbed through skin, or inhaled, at relatively low doses. This is the more severe acute-toxicity category; less severe acute toxicity uses the exclamation mark instead.
Example chemicals: Sodium cyanide, concentrated hydrofluoric acid (also correlates with corrosion).

9. Environment (not OSHA-mandated)

Symbol: A dead fish and a dead tree.
Indicates: Acute or chronic hazards to aquatic life. OSHA does not require this pictogram on U.S. workplace labels because environmental hazards fall outside HCS’s occupational-safety scope, but it is used internationally and can appear on chemicals labeled for global distribution or on transport/EPA-related documentation.
Example chemicals: Certain pesticides and some heavy-metal compounds.

Signal Words: “Danger” vs. “Warning”

Every GHS label carries exactly one signal word (never both), used to communicate relative severity at a glance:

Danger — used for the more severe hazard categories within a hazard class.
Warning — used for less severe hazard categories.

A chemical with multiple hazards uses only the signal word associated with its most severe classified hazard — so “Warning” on a label doesn’t mean the chemical is safe, only that none of its classified hazards reached the “Danger” severity threshold. Some low-hazard chemicals that still require GHS classification may carry no signal word at all if no hazard category triggers one.

Hazard Statements (H-Codes)

A hazard statement is a standardized sentence describing the specific nature of a hazard — the label’s plain-language explanation behind the pictogram. Each is tied to a code beginning with “H” followed by three digits, which makes hazard statements searchable and consistent across languages and manufacturers. The numbering ranges by category:

H2xx — physical hazards (e.g., H225 “Highly flammable liquid and vapour,” H271 “May cause fire or explosion; strong oxidizer”).
H3xx — health hazards (e.g., H314 “Causes severe skin burns and eye damage,” H350 “May cause cancer”).
H4xx — environmental hazards (e.g., H410 “Very toxic to aquatic life with long lasting effects”).

A single chemical’s label typically lists several hazard statements together, one for each classified hazard.

Precautionary Statements (P-Codes)

Precautionary statements tell the reader what to actually do — how to store, handle, and use the chemical safely, what PPE to wear, and how to respond if exposure occurs. Codes begin with “P” and are grouped by function:

P1xx — general precautions (e.g., “Keep out of reach of children”).
P2xx — prevention (e.g., “Wear protective gloves/eye protection/face protection”).
P3xx — response (e.g., “IF ON SKIN: Wash with plenty of soap and water”).
P4xx — storage (e.g., “Store in a well-ventilated place. Keep container tightly closed”).
P5xx — disposal (e.g., “Dispose of contents/container in accordance with local regulations”).

Labels usually show a manufacturer-selected subset of the applicable precautionary statements rather than every possible statement for every hazard, to keep the label legible; the full set is always available on the corresponding SDS.

Product Identifier and Supplier Information

The remaining two required elements are simpler but easy to overlook when scanning a label for hazard information:

Product identifier: the chemical name or code that must exactly match the identifier on the SDS for that chemical — this is what lets you pull the right SDS for the container in front of you.
Supplier identification: name, address, and telephone number of the manufacturer, importer, or responsible party, needed for emergency contact and to trace the chemical’s source.

Reading a Secondary Container Label

The full six-element label described above is what appears on a chemical as shipped from the manufacturer. When lab staff transfer a chemical into a smaller working container (a squeeze bottle, a beaker used for more than one work shift), OSHA’s HazCom rules allow an abbreviated “workplace label” in many cases — typically at minimum the product identifier plus enough hazard information (words, pictograms, or symbols) to convey the hazards, unless the container is used immediately by the person who filled it and emptied by the end of the same shift, in which case no label may be required at all. Secondary-container practices vary by institution’s chemical hygiene plan, so lab-specific policy should always be the controlling reference.

Frequently Asked Questions

What is a GHS label?

A GHS label is the standardized hazard-communication label required on containers of hazardous chemicals under the UN’s Globally Harmonized System of Classification and Labelling of Chemicals, implemented in U.S. workplaces through OSHA’s Hazard Communication Standard. It combines a product identifier, signal word, pictogram(s), hazard statement(s), precautionary statement(s), and supplier information into one standardized format.

How many pictograms does the GHS system have?

Nine: health hazard, flame, exclamation mark, gas cylinder, corrosion, exploding bomb, flame over circle, skull and crossbones, and environment. OSHA’s Hazard Communication Standard requires the first eight on U.S. workplace labels; the environment pictogram is not OSHA-mandated.

What is the difference between “Danger” and “Warning” on a GHS label?

“Danger” signals a more severe hazard category and “Warning” signals a less severe one. A label carries only one signal word, corresponding to its most severe classified hazard, even if the chemical has multiple hazards.

What do the letters and numbers in a hazard statement (like H314) mean?

The “H” indicates it is a hazard statement, and the digits are a standardized code: H2xx codes are physical hazards, H3xx codes are health hazards, and H4xx codes are environmental hazards. The number itself identifies the specific standardized statement, e.g., H314 is “Causes severe skin burns and eye damage.”

Is a GHS label the same as a Safety Data Sheet (SDS)?

No. The label is the at-a-glance summary affixed to the container; the SDS is the full 16-section technical document with detailed information on composition, handling, first aid, toxicology, and more. The product identifier on the label must match the SDS so the two can be connected.

Do all secondary containers in a lab need a full GHS label?

Not always. OSHA permits an abbreviated workplace label for secondary containers in many cases, and containers used immediately by the person who filled it and emptied within the same work shift may not require a label at all. Institutional chemical hygiene plans typically set the specific local rule.

Understanding GHS Labels: Pictograms, Signal Words, and Hazard Statements