What is lux testing?
Lux testing is the on-site measurement of illuminance – the amount of light falling on a surface – using a calibrated illuminance meter (lux meter). One lux equals one lumen spread over one square metre. A lux test records readings across a defined grid of points, calculates the average, minimum and uniformity for each area, and compares those results with the levels recommended for the tasks carried out there.
The output is a written report that shows, room by room, whether the lighting is adequate, where it falls short and what would bring it back into line. For an employer, landlord or facilities manager, that report is the evidence that lighting has been assessed rather than assumed.
Lux testing, lux surveys and lighting surveys
The terms are often used interchangeably. A lux test or lux survey focuses on measured light levels. A broader lighting survey may also look at glare, colour rendering, luminaire condition, controls and energy use. A lux survey is the core of most lighting surveys.
Why lux testing matters
Poor lighting is rarely dramatic, which is why it goes unnoticed. Its effects build up quietly:
- Safety: trips on stairs, misjudged edges, collisions between pedestrians and forklifts, and errors with machinery are all more likely in under-lit or patchy areas.
- Health and comfort: eyestrain, headaches and fatigue are common complaints in offices with low or uneven light, especially for display screen users.
- Productivity and quality: picking errors, inspection misses and slower work follow when people cannot see detail clearly. Both have a direct cost to the business.
- Evidence: insurers, enforcing officers, licensing authorities and tenants increasingly expect documented measurements, not a statement that “the lights work”.
The legal basis in the UK
No single law says “you must carry out a lux test”. Instead, several duties make measured lighting the most practical way to show compliance.
Workplace (Health, Safety and Welfare) Regulations 1992
Regulation 8 requires every workplace to have suitable and sufficient lighting, which should be natural light so far as is reasonably practicable, and suitable and sufficient emergency lighting where people would be exposed to danger if the artificial lighting failed. “Suitable and sufficient” is not defined in lux, so employers rely on recognised guidance to interpret it. More detail is in our guide to the Workplace Regulations.
Management of risk and HSE guidance
Under the Management of Health and Safety at Work Regulations 1999, lighting forms part of the general risk assessment. HSE guidance HSG38 Lighting at work sets out minimum average and minimum point illuminances for broad categories of activity and explains how to assess lighting risks.
Display Screen Equipment Regulations 1992
The Health and Safety (Display Screen Equipment) Regulations 1992 require workstation assessments that include lighting, glare and reflections on screens.
British and European standards
BS EN 12464-1:2021 is the main reference for indoor workplaces. It specifies maintained illuminance, uniformity, glare limits and colour rendering for hundreds of task and activity types. BS EN 12464-2:2024 covers outdoor workplaces, and the CIBSE SLL Code for Lighting and Lighting Guides (such as LG7 for offices) give UK-specific interpretation. Read our summary of BS EN 12464-1:2021.
Emergency lighting and fire safety
The Regulatory Reform (Fire Safety) Order 2005 places duties on the responsible person for emergency escape lighting. BS 5266-1:2025 is the UK code of practice and BS EN 1838:2024 sets the photometric requirements, such as minimum lux on escape routes and in open areas.
How a lux test is carried out
- Scoping: we agree which areas are included, what each is used for and whether emergency lighting is in scope. Activity type determines the target illuminance.
- Conditions: lighting is allowed to stabilise, and daylight is excluded or accounted for so the result reflects the installation rather than the weather.
- Grid measurement: readings are taken on a grid at the height of the task – typically desk height for offices and floor level for corridors, stairs and escape routes – following the method in BS EN 12464-1:2021.
- Analysis: for each area we calculate average illuminance, minimum, and uniformity (Uo, the minimum divided by the average).
- Reporting: results are compared with the relevant standard, with a clear pass, marginal or fail status and practical recommendations.
The full method, including grid spacing and working plane heights, is explained in how is lux measured?
Typical target levels
The table shows selected maintained illuminance and uniformity values from BS EN 12464-1:2021. Targets depend on the specific task, so always check the exact entry for your space.
| Area or task | Maintained illuminance (lx) | Uniformity (Uo) |
|---|---|---|
| Corridors and circulation areas | 100 | 0.40 |
| Warehouse storage areas | 100 | 0.40 |
| Retail sales areas | 300 | 0.40 |
| Classrooms (general) | 300 | 0.60 |
| Packing and dispatch | 300 | 0.60 |
| Offices: writing, reading, data processing | 500 | 0.60 |
Hundreds of other task entries exist, each with its own target.
Which sectors need lux testing?
Any workplace can benefit, but some sectors face more scrutiny or higher risk:
- Offices: display screen work, complaints about glare or headaches, and fit-outs.
- Warehouses and logistics: high racking, narrow aisles, picking accuracy and vehicle movements.
- Factories and industrial sites: machinery, inspection tasks and higher-risk processes.
- Schools, nurseries and universities: classrooms, labs, sports halls and DfE BB90 guidance on daylight and lighting.
- Healthcare and care homes: examination and treatment areas, night-time lighting and HTM/HBN guidance.
- Retail, hospitality and licensed premises: customer safety, back-of-house tasks and licensing conditions.
- Landlords and HMOs: common parts, stairs and escape routes.
- Car parks and external areas: pedestrian routes, ramps and security.
How much does lux testing cost?
Our prices are fixed and published, confirmed before booking. A spot check starts from £90, an office or retail survey for a single floor up to 250 m² from £175, and a warehouse or industrial survey from £320. Emergency escape lighting checks start from £120 and insurance or dilapidations reports from £190. Multi-site work is priced on application. The main cost drivers are floor area, number of distinct rooms, ceiling height and whether emergency lighting is included. Full detail is in how much does lux testing cost?
How often should lux testing be done?
There is no fixed statutory interval. Testing is best triggered by events: a new fit-out or handover, an LED retrofit, a change of use, staff complaints, accidents or near misses, a risk assessment review, or an insurer or landlord request. Many organisations also re-test on a regular cycle as lamp output and surface reflectances decline. Emergency lighting has its own routine of monthly functional and annual full-duration tests under BS 5266-1:2025. Read more in how often should lux testing be carried out?
What happens if the lighting fails?
A failed area is not unusual and is usually straightforward to fix. Common causes are dirty or ageing luminaires, failed lamps or drivers, poor positioning after a layout change, and LED replacements with lower output or a narrower beam. Most of these are inexpensive to put right. As an NICEIC approved contractor, Polarity Electrics can also quote for remedial work if you want it, then re-test to confirm.
Book a lux test
Polarity Lux carries out lux testing across London and the South East, including Hertfordshire, Essex, Kent, Surrey, Berkshire, Buckinghamshire and the wider region. Tell us about your premises and we will confirm a fixed price and a date. Book your lux survey.
Frequently asked questions
Is lux testing a legal requirement in the UK?
There is no law that names lux testing specifically, but the Workplace (Health, Safety and Welfare) Regulations 1992 require suitable and sufficient lighting. Measuring light levels against BS EN 12464-1:2021 and HSE guidance HSG38 is the most reliable way to demonstrate that duty has been met.
What does a lux test measure?
It measures illuminance, the amount of light falling on a surface, in lux. A survey records readings across a grid in each area and reports the average, the minimum and the uniformity against the recommended level for the task.
How long does a lux test take?
A single office floor or small retail unit can usually be measured in a few hours. Larger warehouses, multi-floor buildings or surveys including emergency lighting take longer, and emergency lighting checks are often best done out of hours.
Can I do my own lux test with a phone app?
A phone app can give a rough indication, but phone sensors are not calibrated or cosine and spectrally corrected, so readings are not reliable evidence of compliance. A calibrated illuminance meter and a recognised grid method are needed for a defensible result.
What lux level does an office need?
BS EN 12464-1:2021 recommends a maintained illuminance of 500 lux with a uniformity of 0.60 for writing, typing, reading and data processing tasks in offices.