What BS EN 12464-1:2021 is, and what it is not
BS EN 12464-1:2021 Light and lighting – Lighting of work places – Part 1: Indoor work places is the UK adoption of the European standard for indoor workplace lighting. It replaced the 2011 edition in 2021 and is the benchmark lighting designers, insurers, landlords and enforcing officers use to judge whether a space is properly lit. It is not legislation. The legal duty comes from regulation 8 of the Workplace (Health, Safety and Welfare) Regulations 1992, which requires "suitable and sufficient" lighting. BS EN 12464-1:2021 is the most widely recognised way of showing what "suitable and sufficient" means for a particular task.
It also sits above the HSE's own guidance. HSG38 Lighting at work gives minimum levels for health and safety, for example a 200 lx average for work needing perception of detail. BS EN 12464-1:2021 goes further and sets out what people need for visual comfort and performance as well, which is why a general office is 500 lx rather than 200 lx. Our HSE requirements guide covers the HSG38 figures in detail.
The key lighting criteria in the 2021 edition
The standard's schedule of tasks (Clause 7) gives a row of requirements for each type of area or activity. A compliance survey checks each column, not just the lux figure.
Maintained illuminance: Ēm,r and Ēm,u
Maintained illuminance is the average illuminance on the task area below which the installation must not fall at any point in its life, allowing for lumen depreciation, dirt and lamp failures. The 2021 edition gives two values for every task:
- Ēm,r (required): the minimum maintained illuminance for normal working conditions. This is the figure a survey must meet.
- Ēm,u (modified): a higher value, usually one or two steps up the lux scale, that applies when "context modifiers" are present. It is not an upper limit; it is the level the designer should aim for when conditions are more demanding.
The lux scale runs in steps such as 100, 150, 200, 300, 500, 750 and 1000 lx. Context modifiers that justify moving up include visual tasks that are critical or where errors are costly, unusually small or low-contrast detail, tasks carried out for unusually long periods, low daylight, and occupants with reduced visual capacity, such as older workers. The standard also allows a step down where the detail is unusually large or high in contrast, or the task is very short.
Uniformity (Uo)
Uniformity is the ratio of the minimum to the average illuminance over a surface. For general office work Uo must be at least 0.60. The immediate surrounding area needs Uo ≥ 0.40, and background areas, walls and ceilings need Uo ≥ 0.10. Poor uniformity is one of the most common failures we find after LED retrofits, because new luminaires are often fitted on the old spacing.
Discomfort glare (UGR)
The Unified Glare Rating limit (UGRL) is a maximum value for the installation. Offices and classrooms are typically UGR 19; many industrial and storage tasks allow 22 or 25. UGR depends on the luminaire, its mounting position and the room, so it is normally verified from the design calculation and luminaire photometry, then checked on site for visible problems such as bare high-brightness LEDs in the field of view.
Colour rendering (Ra)
Ra describes how faithfully a light source renders colours. Ra 80 is the minimum for most occupied indoor work, Ra 90 applies to colour-critical tasks and medical examination, and some heavy industrial areas and gangways allow lower values.
Cylindrical illuminance and modelling
Mean cylindrical illuminance (Ēm,z) is the average light falling on a small vertical cylinder, which is a good proxy for how well faces and objects can be seen. It is assessed at 1.2 m above the floor for seated people and 1.6 m for standing people, with Uo ≥ 0.10. The 2021 edition now lists Ēm,z for each task in the schedule rather than in a single general clause, so it is much harder to overlook.
Wall and ceiling illuminance
The 2021 tables also give Ēm,wall and Ēm,ceiling for each task. These control the perceived brightness of the room: a desk can hit 500 lx while the room still feels gloomy if the walls and ceiling are dark. For general office work the standard asks for 150 lx on walls and 100 lx on ceilings.
| Criterion | Office: writing, typing, reading, data processing |
|---|---|
| Ēm,r (required) | 500 lx |
| Ēm,u (modified) | 1000 lx |
| Uo (task area) | 0.60 |
| Ra | 80 |
| UGRL | 19 |
| Ēm,z (cylindrical) | 150 lx |
| Ēm,wall | 150 lx |
| Ēm,ceiling | 100 lx |
Other room types have their own rows in the schedule; see the office lighting standards page for the full office breakdown.
Task area, immediate surroundings and background
The standard does not require a whole room to be lit to the task value. It separates three zones:
- Task area: where the visual task is carried out, lit to Ēm,r or above.
- Immediate surrounding area: a band at least 0.5 m wide around the task. Where the task is 500 lx, the surround should be at least 300 lx; at 750 lx or more, at least 500 lx.
- Background area: a band at least 3 m wide adjoining the immediate surroundings, lit to at least one third of the immediate surrounding value.
Where workstation positions are unknown, as in an open-plan floor that is regularly reconfigured, the sensible approach is to treat the whole working floor as task area.
What changed from the 2011 edition
- Two illuminance values (Ēm,r and Ēm,u) and a formal process of context modifiers, replacing the single maintained value per task.
- Cylindrical, wall and ceiling requirements moved into the task tables, with specific values per task. In practice this raises room brightness compared with many 2011-era designs.
- A new design considerations clause explaining how to apply the requirements to real spaces with multiple activities.
- A new informative annex on the visual and non-visual (circadian) effects of light.
- Revised task values in some areas; for example, classrooms are now listed at 500 lx with controllable lighting, where the 2011 edition gave 300 lx for general classrooms.
- References to energy and Ecodesign, encouraging controls so modified levels are only delivered when needed.
Installations designed to the 2011 edition are not automatically non-compliant, but a survey reported against the current standard may highlight walls, ceilings or cylindrical illuminance that were never assessed before.
BS EN 12464-2:2024: outdoor work places
BS EN 12464-2:2024 replaced the 2014 edition in late 2024 and covers outdoor work places such as yards, loading areas, car parks used by staff, petrol station forecourts, rail sidings, ports and building sites. It uses the same core ideas, maintained illuminance, uniformity and colour rendering, but assesses glare with a glare rating limit (GRL) suited to outdoor viewing rather than UGR. The 2024 edition adds a new environmental zone, E0, for intrinsically dark areas, updates the guidance on flicker and stroboscopic effects and on sustainability, and adds an annex on the reflectance of outdoor materials. It does not cover emergency lighting, which falls under BS EN 1838:2024 and BS 5266-1:2025. Our car park and external lighting surveys are reported against Part 2.
How we test against the standard on site
A BS EN 12464-1:2021 survey is a set of measurements on a defined grid, not a few readings at random desks. We set the calculation grid using the standard's grid-size method for the area being assessed, measure at task height with a calibrated, cosine- and colour-corrected meter, and record walls and vertical planes where the task requires it. Daylight is excluded or recorded separately, and controls are noted so results are repeatable. The full process is explained in how lux is measured. We survey offices, schools, warehouses, healthcare premises and more across London and the South East, including Hertfordshire, Essex, Kent and Surrey.
Book a BS EN 12464 lux survey
If you need evidence that your lighting meets BS EN 12464-1:2021 or 12464-2:2024, whether for an HSE enquiry, a lease, an insurer or staff complaints, book a survey. You receive a clear report showing each area against Ēm,r, uniformity and the other criteria, with practical recommendations where anything falls short.
Frequently asked questions
Is BS EN 12464-1:2021 a legal requirement?
No. The legal duty is regulation 8 of the Workplace (Health, Safety and Welfare) Regulations 1992, which requires suitable and sufficient lighting. BS EN 12464-1:2021 is the recognised benchmark for showing what suitable and sufficient means for a given task.
What is the difference between Em,r and Em,u?
Em,r is the required maintained illuminance that must be met under normal conditions. Em,u is a higher modified value, usually one or two steps up, that applies when context modifiers such as critical tasks, small detail or older occupants are present.
How many lux does BS EN 12464-1:2021 require for an office?
For writing, typing, reading and data processing the required maintained illuminance is 500 lx, with a modified value of 1000 lx, uniformity of at least 0.60, UGR 19 and Ra 80.
Does my 2011-compliant lighting still comply?
Often the task illuminance will still be acceptable, but the 2021 edition adds specific wall, ceiling and cylindrical illuminance values. A survey against the current edition will show whether those are met.
Which standard covers outdoor work areas?
BS EN 12464-2:2024 covers outdoor work places such as yards, loading areas and staff car parks. It replaced the 2014 edition in late 2024.