Overview
ISO 24550:2019 - "Ergonomics - Accessible design - Indicator lights on consumer products" provides design requirements and recommendations for indicator lights (mainly LED) used on household and home appliances to improve visual accessibility for older people and people with visual disabilities. It clarifies what indicator lights are, classifies lighting modes (light‑on, light‑off, blinking, others) and sets out guidance on colour, luminance, size, temporal patterns and location. The standard excludes needs of people who are blind, electronic displays with characters/graphics, and professional/industrial machinery.
Key topics and technical requirements
- Modes of indication: Indicator lights must use clearly recognizable modes - steady on/off, blinking, or gradual changes - each mapped to user-relevant conditions (running, standby, malfunction, etc.).
- Colour guidance: Colours should be noticeable against surroundings; multiple colours must be discriminable; colour must not be the only cue (use shape, location, luminance contrast, temporal patterns). Colour naming should use fundamental colours.
- Luminance recommendations: The standard provides luminance ranges for white indicator lights under photopic and mesopic conditions (tables reference minimum, good‑visibility and glare levels for young, older and low‑vision users). Designers should choose luminance between minimum visibility and glare thresholds and consider automatic adjustment or user control.
- Size and visual angle: Small indicator lights smaller than 20′ of visual angle (≈3 mm viewed at 50 cm) require higher luminance and may alter perceived colour (small‑field tritanopia). Size must be appropriate for expected viewing distance and user visual ability.
- Temporal luminance and blinking: Temporal modulation (blinking, duty cycle and frequency) must be visibly distinct and mapped to meaning (e.g., attention or abnormal condition). The standard addresses suitable temporal patterns to support recognition without causing discomfort.
- Location, marking and alternatives: Placement, labelling (icon/text), alternative presentations and supplementary cues are required to ensure accessible interpretation.
Practical applications
- Product designers and UX/industrial design teams for household appliances (washers, ovens, HVAC, small appliances) use ISO 24550 to specify LED indicator behaviour, colour, brightness and placement.
- Accessibility specialists and ergonomists reference the standard when auditing product interfaces for older adults and low‑vision users.
- Manufacturers incorporate the standard to reduce user errors, improve safety and meet accessibility expectations in consumer electronics and appliances.
Who should use this standard
- Industrial designers, electrical and firmware engineers, product managers, accessibility consultants, compliance officers and standards writers focused on consumer product ergonomics and accessible design.
Related standards
- ISO/IEC Guide 71 (accessibility in standards)
- ISO 17049 (Braille on equipment)
- CIE S 017 (lighting vocabulary)
- ISO/TR 22411 and ISO 24505 (related accessibility and colour guidance)
Keywords: ISO 24550:2019, indicator lights, accessible design, ergonomics, LED indicator, luminance, visual accessibility, older people, low vision.