Overview
EN ISO 22324:2025 - Security and resilience - Emergency management - Guidelines for colour‑coded alert (ISO 22324:2022) provides harmonized guidance on using colour‑coded alerts to inform people at risk and first responders about hazard status and severity. Adopted by CEN from ISO 22324:2022, the standard is applicable to all types of hazard and locations. It focuses on the meaning and practical use of colours in alerting systems rather than on display ergonomics or sign construction (those aspects are covered by ISO 3864‑1).
Key topics
- Core colour spectrum: Use red (danger - take action immediately), yellow (caution - prepare to act), and green (safe - no action required) to express hazard status.
- Supplementary colours:
- Black or purple - indicate fatal danger (can supplement red); black/white checkerboard recommended for screens/LEDs where pure black is non‑luminescent.
- Blue - informational only (not a hazard level).
- Grey - explicitly indicates no information available.
- Level limitations and ordering: Minimize number of hazard levels; use hues between red and green if more than three levels are required; no more than seven colours to avoid confusion. Colour order should provide positional cues (increasing hazard presented left→right or bottom→top).
- Supporting information: Colour coding should be accompanied by understandable supplemental cues - text, numbers, shapes, symbols, size and positional coding - to reduce ambiguity and support accessibility.
- Human factors: Guidance includes considerations for colour blindness and naming conventions; recommended colour specifications (Munsell, CMYK, RGB) are provided in Annex B.
- Normative/reference linkage: Relates to ISO 22300 (vocabulary) and complements ISO 22322 (public warning guidance).
Applications
EN ISO 22324:2025 is practical for organizations that design, operate or regulate alerting systems:
- Public authorities and emergency management agencies - standardized public alerts and community warning levels.
- First responders and incident commanders - consistent internal/field dashboards and status boards.
- Technology providers and UI/UX designers - emergency apps, control-room displays, notification platforms (use colours with supplemental text/symbols).
- Critical infrastructure operators and transport agencies - system status indicators and passenger information.
- Policy makers and planners - developing interoperable alert frameworks and public communication strategies.
Related standards
- ISO 22322 - Public warning guidance (complements colour‑coded alert use).
- ISO 22300 - Vocabulary for security and resilience (normative reference).
- ISO 3864‑1 - Safety signs and colours (ergonomic and sign design - outside scope).
Using EN ISO 22324:2025 helps reduce public confusion, improve timeliness of protective actions, and support interoperable, accessible emergency alerts across platforms and jurisdictions. Keywords: EN ISO 22324:2025, colour‑coded alert, emergency management, public warning, red yellow green, alert standards.
