Radiation Hazard Symbol - Universal Warning Sign for Ionizing Radiation #3073774 (License: Personal Use)

This iconic yellow-and-black triangular symbol, known as the trefoil, was first designed in 1946 at the University of California, Berkeley. It consists of three black blades arranged at 120-degree angles around a central circle, set within an equilateral yellow triangle to maximize visibility and contrast. The design is standardized by ISO 361 and IAEA guidelines for use on containers, doors, and equipment where radioactive sources are present.

Commonly displayed on nuclear facilities, medical imaging rooms, laboratories, transport casks, and radiation therapy equipment. Used to alert personnel and the public to potential exposure risks; matches user intent for safety information, regulatory compliance, or educational content about radiation protection.