Overview
EN ISO 361:2015 (ISO 361:1975) specifies the basic ionizing radiation symbol used to indicate the actual or potential presence of ionizing radiation. Adopted by CEN from ISO, the standard defines the symbol’s intended use, required prominence, and the types of radiation covered (gamma and X‑rays, alpha and beta particles, high‑speed electrons, neutrons, protons and other nuclear particles). It explicitly excludes non‑ionizing phenomena such as sound waves, radio waves and visible/infra‑red/ultra‑violet light. The standard does not set threshold radiation levels for when the symbol must be used.
Key topics and requirements
- Shape and proportions: The symbol’s design and proportions are specified and must be maintained when reproduced. (Prints for reproduction can be obtained from ISO.)
- Size and prominence: The symbol should be as prominent as practical and sized consistently with the equipment or material so it can be read from a safe distance.
- Scope of application: Used to signify actual or potential presence of ionizing radiation or radioactive materials.
- Accompanying information: The basic symbol may be accompanied by additional symbols or words to indicate the type of source, radiation type, limits of occupancy or other precautions - provided these do not detract from the symbol’s clarity.
- Restrictions on use: The symbol shall be displayed only to indicate ionizing radiation hazards as defined in the standard. Additional markings should preferably be limited to internationally adopted symbols for specific purposes.
- No dose criteria: The standard does not define radiation level thresholds or regulatory dose limits for symbol use.
Applications
- Radiation hazard signage on equipment, containers, doors, storage areas and transport packaging for radioactive materials.
- Labels and plates on medical, industrial and research devices that produce ionizing radiation (e.g., X‑ray machines, accelerators, sealed sources).
- Facility and site marking for nuclear installations, laboratories and storage facilities.
- Safety documentation, manuals and training materials where standard graphical identification of ionizing radiation is required.
Who uses this standard
- Radiation protection officers and safety managers
- Equipment manufacturers and designers
- Signage and labeling suppliers
- Regulatory authorities and compliance auditors
- Facility planners in medical, industrial and research sectors
- Standards developers and technical committees
Related standards
EN ISO 361:2015 is the CEN adoption of ISO 361 and sits alongside other international and national guidance on safety signs, graphical symbols and radiation protection. Users should apply EN ISO 361 in combination with local regulations and any industry‑specific signage requirements to ensure compliant and effective hazard communication.
Keywords: ionizing radiation symbol, EN ISO 361:2015, ISO 361, radiation warning symbol, radiation protection, radioactive materials, signage, labeling, safety symbol.
