A chemical pictogram is a standardized graphic symbol printed on the label of a hazardous chemical to give you an immediate visual warning about the type of danger that chemical poses. Each pictogram is a black symbol inside a red diamond-shaped border on a white background, and the system is designed so that anyone, regardless of language, can quickly recognize whether a product is flammable, toxic, corrosive, or otherwise dangerous.
These pictograms are part of the Globally Harmonized System of Classification and Labelling of Chemicals (GHS), a framework developed by the United Nations to standardize chemical hazard communication across countries. In the United States, OSHA requires them on all hazardous chemicals shipped from manufacturers, importers, or distributors.
How Pictograms Work on a Label
Pictograms don’t appear alone. They’re one piece of a required label that also includes a product identifier, a signal word, hazard statements, precautionary statements, and the manufacturer’s contact information. The signal word is either “Danger” (for more severe hazards) or “Warning” (for less severe ones), and it sits alongside the pictograms to help you gauge how serious the risk is.
The red diamond border is a deliberate design choice. On a busy shelf or in a cluttered workspace, that distinctive rotated red square catches your eye faster than plain text. The border must be wide enough to be clearly visible, and the black symbol inside communicates the specific hazard category at a glance. If a chemical has multiple hazards, its label will display multiple pictograms.
The Nine Standard Pictograms
The GHS defines nine pictograms. Eight are mandatory under OSHA’s Hazard Communication Standard, while one (the environment pictogram) is not required in U.S. workplaces but is used internationally. Here’s what each one means and what kinds of chemicals carry it.
Flame
A simple flame icon. This covers flammable liquids, gases, aerosols, and solids, as well as self-reactive chemicals and substances that can self-heat or emit flammable gases when wet. If you see this symbol, the product can ignite under normal conditions or with minimal heat exposure. Common examples include gasoline, acetone, and many spray-can products.
Flame Over Circle
A flame sitting above a circle. This identifies oxidizers: chemicals that may not burn on their own but supply oxygen that can cause or intensify a fire in other materials. Concentrated hydrogen peroxide and certain pool chemicals carry this pictogram.
Exploding Bomb
An image of a bursting object. This marks explosives, self-reactive substances, and organic peroxides that can detonate or explode under certain conditions such as heat, friction, or shock.
Skull and Crossbones
The classic skull symbol. This appears on chemicals that are acutely toxic, meaning a single exposure through swallowing, skin contact, or inhalation can cause serious harm or death. Products carrying this pictogram are at the most dangerous end of the toxicity scale.
Corrosion
An image showing a substance eating through material and skin. This applies to chemicals that cause severe skin burns, serious eye damage, or that corrode metals on contact. Strong acids like hydrochloric acid and strong bases like sodium hydroxide (lye) typically carry this symbol.
Exclamation Mark
A bold exclamation point. This covers a broad range of lower-level health hazards: skin irritation, eye irritation, respiratory irritation, and acute toxicity that’s harmful but less immediately life-threatening than chemicals marked with the skull and crossbones. Many common cleaning products and solvents display this pictogram.
Health Hazard
A silhouette of a person with a starburst on their chest. This is for chemicals that pose serious longer-term health effects. It covers carcinogens (cancer-causing substances), reproductive toxins, respiratory sensitizers, chemicals that damage specific organs with repeated exposure, and substances that are mutagenic (capable of altering DNA). This pictogram signals risks that may not show up immediately but develop over time with repeated contact.
Gas Cylinder
An image of a pressurized gas cylinder. This identifies gases stored under pressure, including compressed gases, liquefied gases, refrigerated liquefied gases, and dissolved gases. The hazard here is both the pressure itself (a ruptured cylinder can become a projectile) and, for refrigerated gases, extreme cold that can cause frostbite.
Environment
A dead tree and dead fish. This pictogram flags chemicals that are toxic to aquatic life or harmful to the ozone layer. OSHA considers this one non-mandatory for U.S. workplace labels, but many international regulations and manufacturers include it voluntarily. You’ll often see it on pesticides and industrial chemicals that should never be released into waterways.
Why Some Chemicals Have Multiple Pictograms
A single chemical can pose several types of hazards at once. Concentrated sulfuric acid, for instance, is both corrosive and can cause serious health effects, so its label may display both the corrosion and health hazard pictograms. When you see multiple red diamonds on a label, each one represents a distinct danger, and you should take precautions for all of them.
There are a few built-in rules to prevent redundancy. If a chemical qualifies for the skull and crossbones (acute toxicity at the most severe level), the exclamation mark for lower-level toxicity won’t also appear, since the more serious warning already covers it. Similarly, the corrosion pictogram takes precedence over the exclamation mark for skin or eye effects.
Where You’ll Find Pictograms
Pictograms appear in two main places. The first is directly on the product label of any hazardous chemical container leaving a manufacturer, importer, or distributor. The second is in Section 2 (Hazard Identification) of a Safety Data Sheet, the detailed document that accompanies hazardous products in workplaces and provides in-depth safety information.
You’ll also encounter them in consumer settings. Many household products like oven cleaners, drain openers, and certain adhesives carry GHS pictograms on their packaging. Even if you never work in a lab or factory, understanding these symbols helps you store, use, and dispose of products safely at home.
Recent Updates to the Standard
OSHA updated its Hazard Communication Standard in May 2024 to align with the seventh revision of the GHS, replacing the previous alignment with the third revision from 2012. The pictograms themselves haven’t changed in appearance, but the update refines how chemicals are classified into hazard categories, which can affect which pictograms appear on a given product’s label. The updated rule took effect on July 19, 2024, so labels on newly manufactured or imported chemicals are now following these revised criteria.