---
title: "Orange oxidising (O) — what it means"
description: "Oxidising agent, under the old European system. What the symbol looks like, what happens if you ignore it, and where its meaning differs by country."
url: https://atoneplace.net/symbol/hazard-eu-orange-oxidising/
site: "At One Place"
---

# Orange oxidising (O)

**Orange oxidising (O): Oxidising agent, under the old European system.**

## What it looks like

A flame over a circle, black on an orange-yellow square, sometimes with the letter O.

## What it means

Replaced one-for-one by the GHS flame-over-circle diamond. The letter code O distinguished it from F for flammable, and the two were routinely confused because both drawings feature a flame — the circle underneath is the difference and it is the important part, since an oxidiser makes other things burn rather than burning itself.

> Defined by Directive 67/548/EEC (repealed). 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 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. |
| Radiation trefoil | Ionising radiation — a radioactive source or a device producing radiation. |
| Laser radiation | Laser radiation — do not look into the beam. |

## Common questions

### What does the orange oxidising (o) symbol mean?

Oxidising agent, under the old European system.

### What does it look like?

A flame over a circle, black on an orange-yellow square, sometimes with the letter O.

## Related pages

- [Flame over circle (GHS03)](https://atoneplace.net/symbol/hazard-ghs-oxidising/)
- [Orange flammable (F, F+)](https://atoneplace.net/symbol/hazard-eu-orange-flammable/)
- [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/)