The “flame over a circle” symbol indicates oxidizing hazardous materials, not ordinary flammables, explosives, or self‑reactives.

What the symbol means

This pictogram is a white diamond with a red border, showing a black circle with flames on top of it.

It is used for substances classified as oxidizing gases, oxidizing liquids, or oxidizing solids.

In plain terms, oxidizers:

  • Do not usually burn by themselves.
  • Can release oxygen or other oxidizing substances.
  • Can cause other materials to catch fire more easily or burn much more intensely.

So, when you see a flame over a circle, the hazardous material it indicates is oxidizers (oxidizing agents).

Information gathered from public forums or data available on the internet and portrayed here.