Hazard Warning Symbols — Complete Guide to Safety Signs & Meanings

Published May 7, 2026

Hazard warning symbols are everywhere — on cleaning products, in laboratories, on road signs, and in workplaces. These symbols are designed to communicate danger instantly, regardless of language barriers. Understanding them can protect your health and safety, and in some cases, save your life.

This guide covers the major hazard symbol systems used worldwide, including GHS pictograms, radiation symbols, biohazard signs, fire safety symbols, and more.

GHS Hazard Pictograms (Globally Harmonized System)

The GHS system was developed by the United Nations to standardize chemical hazard communication worldwide. It uses nine pictograms, each a red diamond with a black symbol on a white background. You will find these on product labels and Safety Data Sheets (SDS).

The Nine GHS Pictograms Explained

1. Flame (Flammable)

This pictogram shows a flame and appears on products that can catch fire easily. This includes flammable liquids (like gasoline), flammable gases (like propane), self-reactive chemicals, and pyrophoric substances that ignite on contact with air.

2. Flame Over Circle (Oxidizer)

A flame appearing above a circle indicates an oxidizing substance. These materials are not necessarily flammable themselves but can cause or intensify a fire by releasing oxygen. Common examples include hydrogen peroxide and ammonium nitrate.

3. Exploding Bomb (Explosive)

The exploding bomb pictogram warns of unstable explosives, self-reactive substances, and organic peroxides. Products with this symbol can detonate or explode under certain conditions like heat, shock, or friction.

4. Corrosion

This symbol shows liquid spilling from two test tubes onto a hand and a metal surface. It indicates severe skin burns, eye damage, or corrosion to metals. Strong acids (like sulfuric acid) and strong bases (like sodium hydroxide) carry this symbol.

5. Gas Cylinder (Compressed Gas)

A simple gas cylinder icon warns of gases stored under pressure. These can explode if heated, and compressed gas can cause frostbite-like injuries if released rapidly. Scuba tanks, propane cylinders, and industrial gas containers display this symbol.

6. Skull and Crossbones (Acute Toxicity)

The classic skull and crossbones indicates substances that are fatal or highly toxic. Even small amounts can cause death or serious harm if swallowed, inhaled, or absorbed through the skin. Pesticides and highly toxic chemicals often bear this symbol.

7. Exclamation Mark (Irritant)

This pictogram is a simple exclamation mark inside the red diamond. It indicates less severe hazards like skin irritation, eye irritation, respiratory tract irritation, and skin sensitization. Products like some cleaning supplies and mild chemicals carry this mark.

8. Health Hazard

A figure with a starburst on the chest represents serious long-term health effects. This includes carcinogens (cancer-causing agents), mutagens, reproductive toxins, and substances that cause organ damage through prolonged or repeated exposure.

9. Environment (Aquatic Toxicity)

This pictogram shows a tree and a dead fish, indicating environmental hazards. It warns that the substance is toxic to aquatic life and may cause long-term damage to water ecosystems.

Radiation Hazard Symbols

The radiation symbol, also known as the trefoil, is one of the most recognizable hazard symbols in the world. It uses a magenta (or black) trefoil on a yellow background to warn of ionizing radiation from radioactive materials or X-ray equipment.

In 2007, the IAEA introduced a supplemental radiation symbol that adds radiating waves, a skull and crossbones, and a running figure to the traditional trefoil. This new symbol is designed to be more intuitive for people who may not be familiar with the trefoil alone.

Biohazard Symbol

The biohazard symbol warns of biological materials that pose a threat to human health. This includes medical waste, microorganisms, viruses, and toxins from biological sources. You will see it in hospitals, laboratories, and on containers of medical waste.

Warning and Caution Signs

Beyond chemical and biological hazards, there are general warning symbols used in workplaces and public spaces:

• ⚠️ Warning — General caution, potential hazard ahead
• ⛔ Prohibited — Do not enter, stop, no access
• 🚫 No Smoking — Smoking prohibited in this area
• 🚷 No Pedestrians — Pedestrian access not allowed
• 🚭 No Open Flames — Fire hazard, no ignition sources

Fire Safety Symbols

Fire safety symbols indicate the locations of fire equipment, escape routes, and fire-related hazards. Common ones include fire extinguisher locations, fire alarm call points, emergency exits, and fire assembly points.

Copy Paste Hazard Symbols

Need hazard symbols for a safety document, training material, or presentation? Here is a complete collection:

How to Read Safety Labels

A proper safety label contains several key elements: the product identifier, the signal word (Danger or Warning), the hazard pictograms, hazard statements describing the nature of the hazard, precautionary statements telling you how to prevent harm, and supplier information. Always read the full label before handling any chemical product.

Understanding these symbols is not just academic — it is practical knowledge that keeps you safe. For more symbol guides, check out our medical symbols guide for healthcare-related symbols and notation.