There is no single number for the cleanroom illuminance standard: ISO 14644 does not specify illuminance; facilities in Taiwan must first comply with Article 313 of the Occupational Safety and Health Facilities Regulations, and precision electronics work then refers to the 1,500 lux in CNS 12112. Mainland China's cleanroom codes set general lighting at 200–500 lx, while Japan's JIS and Europe's EN 12464-1 go up to 1,500 lx for precision electronics work. This article puts the national standards into comparison tables and explains how illuminance calculation, illuminance uniformity and acceptance measurement are done.
What is the cleanroom illuminance standard: the answer in one table
| Your situation | Which document to check | Illuminance |
|---|---|---|
| Legal minimum for factories in Taiwan | Article 313 of Taiwan's Occupational Safety and Health Facilities Regulations | General offices 300 lux or more; precision assembly and fine inspection 500–1,000 lux or more |
| Design target for electronics plants in Taiwan | CNS 12112 Table 5 | Electronic workshops, testing rooms and adjusting rooms 1,500 lux |
| Cleanrooms in mainland China | GB 50073-2013, GB 50472-2008 | Production rooms 200–500 lx; electronics industry 300–500 lx |
| Pharmaceutical cleanrooms | GB 50457-2019, EN 12464-1:2021 | Main work rooms 300 lx; pharmaceutical production in Europe 500 lx |
| Precision electronics work in Japan and Europe | JIS Z 9110, EN 12464-1:2021 | 1,500 lx |
Regulations give the minimum; the design value is set by the visual task of the process: the finer the detail to be seen, the higher the illuminance. Lux (lx) and the "metre-candle" used in Taiwan's regulations are the same unit; for the foot-candle (fc) common in US practice, 1 fc is about 10.76 lx.
Cleanroom illuminance requirements by standard (lx)
Bars are ranges, dots are single values. Cleanroom design codes put general lighting at 200–500 lx; lighting standards for precision electronics work go to 1,500 lx. The pale segment is the EN 12464-1 modified value for poorer visual conditions
Taiwan illuminance standards: Article 313 of the occupational safety regulations and CNS 12112
What is commonly called the "occupational safety law illuminance standard" is found in Subparagraph 6 of Article 313 of Taiwan's Occupational Safety and Health Facilities Regulations: where daylight is insufficient, artificial lighting must make up the illuminance to the values in the table below. Most cleanrooms have no daylight windows, so the requirement applies at all hours.
| Place or type of work (summary of the article's wording) | Illuminance | Type of lighting |
|---|---|---|
| Aisles, stairs, warehouses | 50 metre-candles or more | General lighting |
| Machine and boiler rooms, changing rooms, washrooms | 100 metre-candles or more | General lighting |
| Objects requiring fine discrimination: parts assembly, ordinary inspection and product testing | 200 metre-candles or more | Local lighting |
| Objects requiring precise discrimination: more detailed inspection and precision testing; general offices | 300 metre-candles or more | Local lighting; general lighting for offices |
| Objects requiring very fine discrimination, good contrast: precision assembly, fine inspection | 500–1,000 metre-candles or more | Local lighting |
| Objects requiring extremely precise discrimination, poor contrast: assembly, inspection and testing of extremely fine instruments | 1,000 metre-candles or more | Local lighting |
CNS 12112, Lighting of indoor work places, is the national standard used for design. It gives maintained illuminance, the value below which the average illuminance must not fall during the period of use, and also specifies the glare limit UGR and the colour rendering index Ra.
| CNS 12112 Table 5, electrical industry | Maintained illuminance | UGR limit | Ra |
|---|---|---|---|
| Assembly work: rough | 300 lux | 25 | 80 |
| Assembly work: medium | 500 lux | 22 | 80 |
| Assembly work: fine (e.g. telephones) | 750 lux | 19 | 80 |
| Assembly work: precision (e.g. measuring equipment) | 1,000 lux | 16 | 80 |
| Electronic workshops, testing rooms and adjusting rooms | 1,500 lux | 16 | 80 |
The "1,500–3,000 lux for electronic component manufacturing" often seen online comes from the range table in the old 1987 edition; the 2012 revision replaced it with the single maintained illuminance values in the table above. CNS 12112 also specifies that in continuously occupied areas the maintained illuminance shall not be less than 200 lux.
Cleanroom illuminance standards in mainland China: GB 50073, GB 50472, GB 50034, GB 50457
| Standard | Clause | Area | General lighting illuminance |
|---|---|---|---|
| GB 50073-2013 Code for design of clean room | §9.2.3 | Production rooms in cleanrooms without daylight windows | 200–500 lx |
| GB 50073-2013 | §9.2.3 | Auxiliary rooms, personnel and material cleaning rooms, air locks, corridors | 150–300 lx |
| GB 50472-2008 Code for design of electronic industry clean room | §12.2.1 | Main production rooms | 300–500 lx |
| GB 50472-2008 | §12.2.1 | Auxiliary work rooms, cleaning rooms, air locks, corridors | 200–300 lx |
| GB/T 50034-2024 Standard for lighting design of buildings | Table 5.4.1 | Microelectronic products and integrated circuits, display devices, printed circuit boards | 500 lx (UGR 19, uniformity 0.70, Ra 80) |
| GB/T 50034-2024 | Table 5.4.1 | Pharmaceutical production | 300 lx (UGR 22, uniformity 0.60, Ra 80) |
| GB 50457-2019 Standard for design of pharmaceutical industry clean room | §3.2.6 | Main work rooms | 300 lx |
| GB 50457-2019 | §3.2.6 | Auxiliary work rooms, corridors, air locks, personnel and material cleaning rooms | 200 lx |
Both GB 50073-2013 §9.2.4 and GB 50457-2019 §11.2.5 require a general lighting illuminance uniformity of no less than 0.7. GB 50073-2013 §9.2.5 also requires standby lighting in cleanroom buildings; the reference given in the clause commentary is no less than 1/10 of normal lighting for general areas.
Cleanroom lighting standards in Japan, Europe and the United States
| Source | Applicable work | Illuminance |
|---|---|---|
| JIS Z 9110 General rules of recommended lighting levels (Japan) | Very precise visual tasks in precision machinery and electronic component manufacturing | 1,500 lx |
| Cleanroom design data from Japanese lighting manufacturers | Work surface in general cleanrooms | about 1,000–2,000 lx |
| EN 12464-1:2021 Table 19 (Europe) | Fine assembly (telephones, radios, computers) | 750 lx, uniformity 0.70, UGR 19 |
| EN 12464-1:2021 Table 19 | Precision assembly (measuring equipment, printed circuit boards) | 1,000 lx, uniformity 0.70, UGR 16 |
| EN 12464-1:2021 Table 19 | Electronic workshops, testing, adjusting | 1,500 lx, uniformity 0.70, UGR 16 |
| EN 12464-1:2021 Table 18 | Pharmaceutical production | 500 lx, uniformity 0.60, UGR 22 |
| NASA MSFC-STD-246E (United States, 2019) | Cleanroom general lighting | 750–860 lx |
| NASA MSFC-STD-246E | Work positions with high contamination sensitivity | about 1,100 lx; task lights may be used to make up the level |
EN 12464-1 has no row for "cleanrooms"; the values have to be matched by type of task. The 2021 edition also gives a modified value one step higher for use when visual conditions are poorer; for electronic workshops, for example, it rises from 1,500 lx to 2,000 lx.
Do ISO 14644 and GMP specify illuminance? No numerical values
| Document | Lighting requirement | lux value |
|---|---|---|
| ISO 14644-4:2001 Annex F | Illuminance levels and uniformity for each area should be specified; colour rendering is specified by the purchaser; luminaires must not release contamination, and in unidirectional-flow areas they should minimise turbulence | None; agreed between purchaser and supplier |
| ISO 14644-3 (test methods) | Illuminance is not among the test items | None |
| US 21 CFR 211.44 | Adequate lighting shall be provided in all areas | None |
| EU GMP Part 1, Chapter 3 | Lighting should be appropriate; production areas should be well lit, particularly where visual on-line controls are carried out | None |
| WHO GMP (TRS 986, Annex 2) | Same direction as EU GMP | None |
So "compliant with ISO 14644" or "GMP compliant" does not mean the illuminance reaches any particular figure; illuminance has to be written separately into the user requirements specification (URS) and the contract. For how ISO classes are defined, see the ISO 14644-1 cleanroom classification table.
Cleanroom lighting design: general lighting plus local lighting
High illuminance values refer to the work surface, not the whole room. Article 313 of Taiwan's Occupational Safety and Health Facilities Regulations classes all work at 500 metre-candles or more as local lighting, and GB/T 50034-2024 also notes for some precision tasks that local lighting should be added. The common practice is to bring general lighting to 300–500 lx and then use task lights at inspection stations, alignment stations and microscope stations to reach 1,000–1,500 lx.
Where the fixtures go depends on the ceiling type. When the ceiling is fully covered with FFUs there are no empty cells for recessed lights, and teardrop lights hung below the T-bar grid between two filters are the common solution for such areas; for the differences between the four teardrop light constructions, see What a teardrop light is, and 4 constructions on the market compared.
| Ceiling type | Where the fixtures go | Design notes |
|---|---|---|
| Unidirectional-flow area with full FFU coverage (ISO 4–6) | Teardrop lights below the T-bar grid, between two filters | One row of lights per grid line; the upper limit of illuminance must be calculated first |
| Ceiling with HEPA terminal diffusers and blank panels (ISO 7–8) | Recessed or surface-mounted cleanroom fixtures | When recessed, the installation gap must be reliably sealed (GB 50073-2013 §9.2.2) |
| Sandwich-panel ceiling without a grid | Surface-mounted fixtures | Smooth housing that does not collect dust and can be wiped |
Illuminance calculation formula: using the lumen method to work out the number of fixtures
The lumen method formula is: Number of fixtures = target illuminance × area ÷ (lumens per fixture × utilisation factor × maintenance factor). The utilisation factor is the proportion of the light emitted by the fixtures that reaches the work surface; the maintenance factor is the reduction that accounts for lumen depreciation and dirt accumulation. Using the assumptions of a utilisation factor of 0.6 and a maintenance factor of 0.8, the table below gives the total luminous flux and the number of fixtures needed per 100 m²:
| Target illuminance | Total luminous flux needed per 100 m² | Fixtures at 2,100 lm each | Fixtures at 4,500 lm each |
|---|---|---|---|
| 300 lx | 62,500 lm | 30 fixtures | 14 fixtures |
| 500 lx | about 104,000 lm | 50 fixtures | 24 fixtures |
| 750 lx | about 156,000 lm | 75 fixtures | 35 fixtures |
| 1,000 lx | about 208,000 lm | 100 fixtures | 47 fixtures |
| 1,500 lx | 312,500 lm | 149 fixtures | 70 fixtures |
The maintenance factor is not a fixed value: lighting manufacturers' handbooks cite the CIE 97 reference values, about 0.8 for very clean environments such as cleanrooms; for LED fixtures with L80 lumen maintenance it works out at about 0.71, and only L90 comes close to 0.8. EN 12464-1:2021 requires the designer to state the maintenance factor used and its assumptions, and the initial illuminance equals the maintained illuminance divided by the maintenance factor. This table is only a first estimate; the final layout should be run in lighting software using the floor plan and the ceiling grid drawing.
What an illuminance uniformity of 0.7 means
Illuminance uniformity is the minimum illuminance on the work surface divided by the average illuminance; the closer the value is to 1, the more uniform the lighting. Uo in EN 12464-1 and U0 in GB 50034 share this definition; mainland China's cleanroom codes require no less than 0.7, and EN 12464-1:2021 also gives 0.70 for precision electronics work. Common causes of poor uniformity are fixture rows spaced too far apart, or equipment and racks blocking the light.
Illuminance testing and acceptance: how illuminance is measured
| Item | Method | Basis |
|---|---|---|
| Measurement height | Measure at work-surface height; if not specified, take about 0.8 m above the floor | JIS C 7612 (80 ± 5 cm); the NEBB specification template uses 915 mm |
| Measurement points | Draw a grid based on the room dimensions and fixture layout; the acceptance points match the grid used in the design calculation | EN 12464-1:2021 §8.2 |
| Average illuminance | For each unit area take the average of the readings at the four corners (four-point method), then calculate the average for the whole room | JIS C 7612 |
| Lamp warm-up | Fluorescent and high-intensity discharge lamps are lit for at least 2 hours before measurement | NEBB specification template |
| Measurement conditions | Measure under actual working conditions, with general lighting and task lights switched on as usual | NEBB specification template |
| Instrument | Illuminance meter calibrated every 12 months | NEBB specification template |
| Acceptance criterion | Compare the measured average illuminance and uniformity with the design values; there is no universal pass value in lux | NEBB specification template |
In IEST-RP-CC006 the illuminance test is an optional, secondary test, and ISO 14644-3 does not include it at all, so if it is to be verified the contract must state the measurement height, grid, target illuminance and uniformity. Documents differ on the measurement height (760 mm, 0.8 m and 915 mm are all found), so the contract governs.
Yellow-light area lighting: no standard illuminance value
Yellow-light areas (photolithography areas) must filter out the short wavelengths that would expose the photoresist; resist suppliers recommend blocking everything below 500 nm. No standard can be found that gives an illuminance value for yellow-light areas; ISO 14644-4:2001 lists wavelength restrictions on lighting as an item to be agreed between purchaser and supplier. Filtering lowers the illuminance, so the design calculation should use the luminous flux after filtering; for AMC control in yellow-light areas, see EUV lithography AMC control in practice.
6 things to confirm before design and purchasing
- 1Which standard applies: the Taiwan legal minimum, CNS 12112, or a GB, JIS or EN standard specified by the customer.
- 2The target maintained illuminance and uniformity for each area, and whether the figure covers general lighting only or includes local lighting.
- 3The utilisation factor and maintenance factor used in the calculation, and whether the fixtures' lumen maintenance is L80 or L90.
- 4Whether there are wavelength restrictions (yellow-light areas) and colour rendering requirements; JIS Z 9110 requires Ra 90 or higher for tasks where colour matters.
- 5Whether the measurement height, grid and acceptance criterion for acceptance testing are written into the contract.
- 6Who designs the standby lighting and the evacuation lighting.
For how to choose the other equipment on a cleanroom ceiling, see the cleanroom equipment series and the FFU selection guide.
FAQ
Q: What is the cleanroom illuminance standard in lux?
There is no single number. In Taiwan the legal minimum is Article 313 of the Occupational Safety and Health Facilities Regulations (500–1,000 lux or more for precision assembly and fine inspection), and CNS 12112 gives a maintained illuminance of 1,500 lux for electronic workshops and testing rooms; in mainland China, GB 50073-2013 gives 200–500 lx for cleanroom production rooms. The actual design value is set by the visual task of the process.
Q: What factory illuminance does Taiwan's occupational safety law require?
Article 313 of Taiwan's Occupational Safety and Health Facilities Regulations grades illuminance by how fine the work is: 50 for aisles and warehouses, 100 for machine rooms and changing rooms, 200 for parts assembly and ordinary inspection, 300 for precision testing and general offices, 500–1,000 for precision assembly and fine inspection, and 1,000 metre-candles or more for assembly and inspection of extremely fine instruments. A metre-candle is the same as a lux.
Q: Does ISO 14644 specify cleanroom illuminance?
No. ISO 14644-4:2001 Annex F only requires that illuminance levels and uniformity for each area be specified, and the test items in ISO 14644-3 do not include illuminance either. Illuminance has to be written into the user requirements specification and the contract.
Q: How much illuminance does a GMP pharmaceutical cleanroom need?
US 21 CFR 211.44, EU GMP and WHO GMP all require only that lighting be adequate or appropriate, with no lux value. Design values that can be cited are 300 lx for main work rooms in GB 50457-2019 and 500 lx for pharmaceutical production in EN 12464-1:2021. For filter requirements in GMP cleanrooms, see the complete guide to HEPA compliance in GMP pharmaceutical plants.
Q: At what height should illuminance be measured?
At work-surface height. If not specified, JIS C 7612 takes 80 ± 5 cm above the floor and the NEBB specification template states 915 mm; what the contract says governs.
Q: On a ceiling fully covered with FFUs, can teardrop lights reach 1,500 lux?
Hardly with general lighting alone. Estimated with single tubes at 2,100 lm, a utilisation factor of 0.6 and a maintenance factor of 0.8, one row of single-tube fixtures along every 1200 mm grid line gives about 700 lx; to go higher, use the twin-tube version, add more rows, or add local lighting at the workstation.
