Lux Levels at Work: What HSE Recommends, and How to Log Light Continuously
TL;DR: The law requires suitable and sufficient lighting at work, and HSE’s guidance HSG38 turns that into lux levels: from 20 lux average and 5 lux minimum on circulation routes up to 500 lux average and 200 lux minimum for fine detail work, with offices at 200 and 100. It also limits the ratio between adjacent areas to 5:1 or 10:1. A one-off survey shows lux levels on the day; a LoRaWAN light sensor such as the Milesight EM500-LGT logs them continuously as daylight, ageing lamps and schedules change.
Last updated: 14 September 2026
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Key takeaways
- The Workplace (Health, Safety and Welfare) Regulations 1992 require every workplace to have suitable and sufficient lighting, by natural light as far as reasonably practicable.
- HSE’s guidance HSG38, Lighting at work, sets lux levels as an average for the work area and a minimum measured value at any point in it.
- Recommended averages run from 20 lux for circulation routes to 200 lux for offices and 500 lux for fine detail work.
- HSG38 limits the ratio between adjacent areas to 5:1, or 10:1 where areas are separated but people move between them often.
- The Milesight EM500-LGT measures 0 to 100,000 lux to ±3% at 1 lux resolution, on a battery rated for 10 years at a 10 minute interval.
What lux levels does HSE recommend?
HSE recommends lux levels by how much detail a task needs, giving an average illuminance for the work area and a minimum measured illuminance for any position in it. The figures come from the table in HSG38, Lighting at work, HSE’s guidance on meeting the legal duty for suitable and sufficient lighting.
| Activity | Typical locations in HSG38 | Average (lux) | Minimum measured (lux) |
|---|---|---|---|
| Movement of people, machines and vehicles | Lorry parks, corridors, circulation routes | 20 | 5 |
| Movement in hazardous areas, rough work | Construction site clearance, loading bays, bottling and canning plant | 50 | 20 |
| Work needing limited perception of detail | Kitchens, factories assembling large components, potteries | 100 | 50 |
| Work needing perception of detail | Offices, sheet metal work, bookbinding | 200 | 100 |
| Work needing perception of fine detail | Drawing offices, electronic assembly, textile production | 500 | 200 |
HSG38 explains why both columns matter: relying on the average alone can leave some areas darker, which may endanger workers. The minimum is the lowest level it recommends anywhere in the work area for health and safety, so the dark corner of a warehouse aisle counts as much as the bright middle.
What does the law actually require?
The law requires suitable and sufficient lighting, not a specific number. Regulation 8 of the Workplace (Health, Safety and Welfare) Regulations 1992 says every workplace shall have suitable and sufficient lighting, that it shall be by natural light so far as is reasonably practicable, and that emergency lighting is needed where people would be specially exposed to danger if artificial lighting failed.
That is where the recommended lux levels in HSG38 come in. They are HSE’s guidance for judging whether lighting is suitable and sufficient for the work being done. They are not the only reference; HSG38 itself points to the CIBSE Code for lighting for performance-related levels.
What is the ratio rule?
The ratio rule for lux levels stops people walking from a bright area into one so much darker that their eyes cannot adjust in time. HSG38 recommends a maximum illuminance ratio of 5:1 between a task and its surroundings or between adjacent working areas, and 10:1 where two areas are separated by a barrier but people move between them often.
HSG38 gives a worked example. An interior lit to 500 lux has an adjacent area where only movement happens, so the table suggests 20 lux there. But 500 to 20 is a ratio of 25:1, far above 10:1, so the adjacent area should be lit to 50 lux, at least nearest the doorway, with a transition zone before dropping to 20 lux further away.
This is exactly the situation at a warehouse door onto a loading bay, and it is one of the easiest faults to miss, because each area can meet its own row in the table while the step between them does not.
Why measure lux levels continuously?
A lighting survey with a hand-held meter records lux levels on one day, at one time, with the lamps as they were. Continuous measurement shows what happens the rest of the year, which is when most lighting problems appear.
Four things change lighting after the survey. Daylight varies by hour and season, so a space that meets its level on a sunny afternoon may not at 7am in December. Luminaires get dirty and lamps age, so output falls gradually. Individual fittings fail and nobody reports them. And schedules change, especially once lighting is switched by a controller such as the WS558, where a timer set for summer can leave a winter morning shift in the dark.
A light sensor at the critical points turns those changes in lux levels into data. It shows whether the minimum is held through the darkest part of the working day, and it gives evidence when a complaint about poor lighting arrives.
How does the EM500-LGT measure lux?
The Milesight EM500-LGT is a LoRaWAN light sensor with its sensing head on a 3 m cable, so the head sits at the task while the transceiver mounts nearby. It measures from 0 to 100,000 lux with ±3% accuracy and 1 lux resolution, and reports over LoRaWAN at the interval you set.
| EM500-LGT datasheet | |
|---|---|
| Range | 0 to 100,000 lux |
| Accuracy | ±3% |
| Resolution | 1 lux |
| Sensor cable | 3 m |
| Protection | Transceiver IP67, light sensor IP65 |
| Battery | 19,000 mAh, around 10 years at a 10 minute interval |
| Configuration | NFC, USB-C or downlink |
| Features | Threshold alarm, storage of 1,000 readings, retransmission |
The range covers all the lux levels in HSG38, from a 5 lux corridor minimum to full daylight, and 1 lux resolution is fine enough for the lowest rows of the HSG38 table. A threshold alarm flags readings that fall below a level you set, so a failing zone stands out without anyone reading charts. See the EM500-LGT product page for full details.
Where should a lux sensor go?
Put a lux sensor where lux levels are most likely to fall short, at the task and facing the light the task receives. One sensor measures one point, so choose the points that matter rather than trying to cover every square metre.
- The darkest position a person works in. The minimum measured value is set by the worst spot, not the average.
- Doorways between bright and dark areas. This is where the 5:1 and 10:1 ratio rules are most often broken.
- Spaces that depend on daylight. Near rooflights and windows, where the morning and winter readings differ most from the afternoon survey.
- Areas on switched or dimmed schedules. To prove the schedule never leaves people below their level.
- Clear of shadows and obstructions. A sensor behind a rack upright or under a shelf measures the shadow, not the room.
What are the limits of a lux sensor?
A lux sensor logs light at one point, so it complements a lighting survey rather than replacing it. The average illuminance in HSG38 describes a whole work area, which needs a grid of measurements with a calibrated meter.
It also measures only one property of light. Glare, flicker and colour rendering all affect whether lighting is suitable, and none of them shows up in a lux reading. Plants are a separate case: lux is weighted to the human eye, so for growing, a PAR sensor is the right instrument. Finally, any sensor drifts, so check it against a calibrated meter periodically if its readings support compliance decisions.
Frequently asked questions
What lux level is required in an office?
HSE’s HSG38 recommends an average of 200 lux and a minimum measured illuminance of 100 lux for work requiring perception of detail, which includes offices. The legal duty is for suitable and sufficient lighting.
What lux levels does HSE recommend for corridors?
HSG38 recommends an average of 20 lux and a minimum of 5 lux for movement of people, machines and vehicles, including corridors, circulation routes and lorry parks.
Is there a legal minimum lux level in the UK?
No single legal figure applies. The Workplace Regulations 1992 require suitable and sufficient lighting, and HSE’s HSG38 gives recommended average and minimum lux levels for different types of work.
How accurate is the Milesight EM500-LGT?
The datasheet gives ±3% accuracy across 0 to 100,000 lux, with 1 lux resolution. Check it against a calibrated meter periodically if it supports compliance decisions.
Can a light sensor replace a lighting survey?
No. A sensor logs lux levels at one point over time. A survey measures a grid across the whole area to establish the average and minimum. The two work best together.
Measure the dark corner, not the bright middle
Lux levels at work are judged by the average and, just as much, by the minimum and the step between areas. A survey sets the baseline; a light sensor at the critical points shows whether it holds through dark mornings, dirty fittings and new schedules.
See the EM500-LGT on Indiott, read our guide to smart lighting control, or see how the same sensor tracks light exposure in our archive environment monitoring kit.
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