Radioactive Symbol

Meaning

The radioactive symbol ☢ is the international trefoil: three blades around a small circle. It warns of ionizing radiation from radioactive materials and certain equipment. It was designed in 1946 at the University of California, Berkeley, and later standardized so workers could recognize danger at a glance.

Copy ☢ (U+2622) or ☢️ when you need the real warning character in a document, map key, or educational graphic. Using it as a fashion or gamer badge is common, but it still reads as “hazard” first. It is not the same as the atom ⚛, the biohazard ☣ sign, or a periodic-table element code.

For chemistry homework about isotopes and neutron counts, see the atom page — those answers use letter symbols like Ga, not the trefoil. Teachers and safety trainers should pair ☢ with clear wording (“ionizing radiation”) so students do not confuse it with a comic-book logo.

On packaging and transport placards, color and shape rules may apply beyond the Unicode character alone. The text glyph is still useful in notes, slides, and UI mockups when you need the recognizable mark without drawing a full placard.

Origin

1946 radiation-lab warning design; later adopted as the ISO ionizing-radiation trefoil used worldwide on doors, containers, and equipment.

Cultural variations

Laboratories, transport placards, and nuclear sites use it as a legal-style warning. Pop culture uses it for dystopia, metal music, and “danger cool.” In safety-critical writing, keep the meaning literal. Streetwear that borrows ☢ inherits that hazard association even when the wearer intends only style.