- Addressable emergency lighting
- A system where each emergency fitting reports its status to a central panel, so faults show up without walking the building.
- Batten
- A long, surface-mounted linear fitting, traditionally holding fluorescent tubes; LED battens replace them as complete luminaires.
- BS 5266-1
- The UK code of practice for emergency lighting of premises. The current edition is BS 5266-1:2025.
- BS 7671
- The IET Wiring Regulations. The current version is BS 7671:2018+A4:2026, still the 18th Edition.
- BS EN 1838
- The standard for emergency lighting light levels. BS EN 1838:2024 sets at least 1 lux across the width of an escape route.
- BS EN 12464-1
- The standard for lighting indoor workplaces, which sets maintained illuminance, glare and uniformity targets for tasks such as office work (500 lux).
- BS EN 50172
- The standard for installing, verifying, operating and testing emergency lighting, including monthly and annual tests.
- Circuit-watt
- The total power drawn by a lighting circuit, including drivers and control gear, used when measuring efficacy for Building Regulations.
- Colour rendering (CRI or Ra)
- How faithfully a light source shows colours compared with a reference. Higher values suit retail, healthcare and workshops.
- Colour temperature
- How warm or cool white light looks, measured in kelvin (K). Around 3000 K looks warm; 4000 K is neutral and common in offices.
- DALI
- Digital Addressable Lighting Interface, a control standard that lets each fitting be dimmed, grouped and monitored individually.
- Daylight harvesting
- Automatically dimming electric lighting when there is enough daylight, using a daylight sensor.
- Driver
- The electronic unit that powers an LED fitting, the LED equivalent of a fluorescent ballast.
- Efficacy
- Light output per watt of power, in lumens per watt. Building Regulations set minimum efficacy for new lighting.
- Electrical Installation Certificate (EIC)
- The certificate issued under BS 7671 for new installations or circuits.
- EICR
- Electrical Installation Condition Report, a periodic inspection of an existing installation.
- Escape route lighting
- Emergency lighting that lets people find and use escape routes safely when the normal supply fails.
- High bay
- A fitting designed for tall spaces, usually above about six metres, such as warehouses and factories.
- High-risk task area lighting
- Emergency lighting that lets people make a dangerous process safe before they leave.
- IK rating
- A rating for a fitting's resistance to impact, important in sports halls and vulnerable areas.
- IP rating
- Ingress Protection rating, showing resistance to dust and water. External and kitchen fittings need suitable IP ratings.
- LENI
- Lighting Energy Numeric Indicator, an alternative way of showing lighting energy compliance based on annual energy use per square metre.
- Lumen
- A measure of the total light given out by a source.
- Lux
- A measure of light falling on a surface: one lumen per square metre. Light meters read in lux.
- Maintained emergency lighting
- Emergency fittings that stay lit all the time and continue when the supply fails, typical for exit signs.
- Maintained illuminance
- The light level a design must not fall below over its life, allowing for dirt and ageing.
- MEWP
- Mobile elevating work platform, such as a scissor or boom lift, used for high-level work.
- Non-maintained emergency lighting
- Emergency fittings that only light when the normal supply fails.
- Open area (anti-panic) lighting
- Emergency lighting that lets people move safely from large open spaces to an escape route.
- Part-night dimming
- Reducing external lighting to a lower level during the quietest hours of the night.
- Photocell
- A sensor that switches lighting on at dusk and off at dawn.
- PIR sensor
- Passive infrared sensor that detects movement and switches lights on or keeps them on.
- Rated duration
- How long emergency lighting must run on battery, set by design and risk assessment; three hours is common.
- Self-test emergency lighting
- Fittings that run their own functional and duration tests and show a status indicator.
- UGR
- Unified Glare Rating, a measure of discomfort glare from a lighting installation. Lower is better for offices.
- WEEE
- Waste electrical and electronic equipment. Old fittings and fluorescent tubes must be disposed of through proper routes.
Lighting glossary
Plain-English definitions of the terms you will see in quotes and standards.