☢️ Radioactive

Unicode lists ☢️ Radioactive among the warning signs in the Symbols group. Typical contexts are sign.

You can drop ☢️ into chats, social posts, headlines or a bio. On SmileyZone it is filed under Warnings. The character has been part of the standard since 2015 (Emoji 1.0). Its code point is U+2622.

• A single ☢️ is often enough to set the tone.
• Fits messages about sign.
• Often seen near 🔞 No One Under Eighteen, 📵 No Mobile Phones and ☣️ Biohazard.

The radiation sign was created in 1946 at the University of California; the colouring was initially magenta on blue, later black on yellow. It is one of the few symbols intended to be understood worldwide without translation.

That is precisely the concern of nuclear semiotics: how do you warn people ten thousand years from now about a repository when no present-day language survives? In 2007 an additional sign was introduced, adding a skull and a fleeing figure.

• ☢️⛔ – Radioactive and No Entry
• ☢️🚳 – Radioactive with No Bicycles
• ☢️🔞 – Radioactive plus No One Under Eighteen
• ☢️📵 – Radioactive and No Mobile Phones
• ☢️🚫 – Radioactive with Prohibited
• ☢️🚸 – Radioactive plus Children Crossing

Easy to mix up with 🔞 No One Under Eighteen, 📵 No Mobile Phones or ☣️ Biohazard. They sit in the same Unicode subgroup and look similar at small sizes, so it is worth checking the name before sending.