---
title: "Radiation trefoil — what it means"
description: "Ionising radiation — a radioactive source or a device producing radiation. What the symbol looks like, what happens if you ignore it, and where its meaning differs b"
url: https://atoneplace.net/symbol/hazard-radioactive/
site: "At One Place"
---

# Radiation trefoil

**Radiation trefoil: Ionising radiation — a radioactive source or a device producing radiation.**

☢

## What it looks like

Three black wedges radiating from a central circle, on a yellow background.

## What it means

The wedges represent radiation coming from an atom at the centre. It marks sources ranging from the trivial to the lethal, which is why a second symbol exists: the 2007 ISO supplementary sign, showing the trefoil with waves, a skull and a running figure, is placed directly on dangerous sealed sources beneath their housing, where someone dismantling the device for scrap would meet it. Domestic smoke alarms containing americium-241 carry the trefoil and are not hazardous in normal use.

> Defined by ISO 361 / ISO 21482. Where a symbol differs between standards, the difference is described above rather than resolved — both versions are in circulation on real labels.

## Other hazard warnings symbols

| Symbol | Means |
| --- | --- |
| Exploding bomb (GHS01) | Explosive, self-reactive, or an organic peroxide that can explode. |
| Flame (GHS02) | Flammable — or a substance that heats up, ignites in air, or gives off flammable gas when wet. |
| Flame over circle (GHS03) | Oxidising — it will feed a fire, including one that has nothing else to burn with. |
| Gas cylinder (GHS04) | Gas under pressure — compressed, liquefied, refrigerated or dissolved. |
| Corrosion (GHS05) | Causes severe skin burns and eye damage, or corrodes metal. |
| Skull and crossbones (GHS06) | Acute toxicity — fatal or toxic in small amounts by swallowing, skin contact or inhalation. |
| Exclamation mark (GHS07) | Irritant, skin sensitiser, harmful if swallowed or inhaled, or may cause drowsiness — the lower-severity hazards. |
| Health hazard (GHS08) | Serious long-term health effects — cancer, genetic damage, harm to fertility or the unborn child, organ damage, asthma from inhalation, or fatal if swallowed and it enters the airways. |
| Environment (GHS09) | Hazardous to the aquatic environment — toxic to fish and other water life. |
| Orange explosive (E) | Explosive, under the old European system. |
| Orange oxidising (O) | Oxidising agent, under the old European system. |
| Orange flammable (F, F+) | Highly flammable (F) or extremely flammable (F+), under the old European system. |
| Orange toxic (T, T+) | Toxic (T) or very toxic (T+), under the old European system. |
| Orange harmful or irritant (Xn, Xi) | Harmful (Xn) or irritant (Xi), under the old European system. |
| Orange corrosive (C) | Corrosive, under the old European system. |
| Orange dangerous for the environment (N) | Dangerous for the environment, under the old European system. |
| NFPA 704 fire diamond | A US placard telling emergency responders how a stored chemical behaves in a fire. |
| Biohazard | Biological material that can cause disease — blood, cultures, clinical waste. |
| Laser radiation | Laser radiation — do not look into the beam. |

## Common questions

### What does the radiation trefoil symbol mean?

Ionising radiation — a radioactive source or a device producing radiation.

### What does it look like?

Three black wedges radiating from a central circle, on a yellow background.

## Related pages

- [Biohazard](https://atoneplace.net/symbol/hazard-biohazard/)
- [Exploding bomb (GHS01)](https://atoneplace.net/symbol/hazard-ghs-explosive/)
- [Flame (GHS02)](https://atoneplace.net/symbol/hazard-ghs-flammable/)
- [Flame over circle (GHS03)](https://atoneplace.net/symbol/hazard-ghs-oxidising/)
- [Gas cylinder (GHS04)](https://atoneplace.net/symbol/hazard-ghs-gas-cylinder/)
- [Corrosion (GHS05)](https://atoneplace.net/symbol/hazard-ghs-corrosive/)
- [Skull and crossbones (GHS06)](https://atoneplace.net/symbol/hazard-ghs-toxic/)
- [Exclamation mark (GHS07)](https://atoneplace.net/symbol/hazard-ghs-irritant/)
- [Health hazard (GHS08)](https://atoneplace.net/symbol/hazard-ghs-health/)
- [Environment (GHS09)](https://atoneplace.net/symbol/hazard-ghs-environment/)
- [Orange explosive (E)](https://atoneplace.net/symbol/hazard-eu-orange-explosive/)

## Sources

- Official vendor product documentation — At One Place (/about/)