How is Lux Level Measured?

Dear All,
Please guide me about what is Lux level? How it is measured? What are its limits for manufacturing area???


The lux (symbol: lx) is the SI unit of illuminance and luminous emittance measuring luminous power per area. It is used in photometry as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface. It is analogous to the radiometric unit watts per square metre, but with the power at each wavelength weighted according to the luminosity function, a standardized model of human visual brightness perception. In English, “lux” is used in both singular and plural.

In the EU-GMP guide you can find general requirements on the ligthing or the light fittings in items 3.3, 3.10 or 3.16.

Normal industrial practice is 200- 250 LUX in normal working areas.

500 to 600 Lux in Inspection area

650 to 700 LUX in documentation areas.

You must not have more LUX as it might add to heat in cleanroms and thus it generates more load on HVAC systems to keep them with in the controlled temeratures as per cGMP Guidance.

footcandles (lumens/square foot) x 10.764 = lux (lumens/square meter)

Dear Sir,
Thank you for your valuable information regarding LUX level.

Good explanation Mr. Durga,

In addition to post Periodic Evaluation of Lux level is also requirement from d/f regulatory agencies.

Hi Prasadji,

I am looking for the exact vaue lux you’ve mentioned, into the EU GMP, but not able to find.
Please help me with chapter no., is value mentioned clearly ??

Sandip V. patel

There isn’t an exact value stated in EU GMP:

The chapter referred to above is here:

Maybe if you clarified why you were after this (is it for a URS or a qualification?) then it might be easier to answer rather than pointing you in the direction of relevant regulations

Qualification purpose. Even what if it will for URS.


I think DURGA_PRASAD’s response above does tell you everything you need to know.
There is no specified requirement in any regulations, though he has given you approximate industry standards.

In all reality, it’s up to you as to what lux level you’d like in your facility (unless this has been stated in your URS).
If on the other hand you’re trying to qualify (or re-qualify using new criteria) an existing area, then you’ll need a lux-meter and take measurements at various locations in the facility. This will give you an idea of whether the light levels meet the specification or not. There are companies that will do this for you and provide you with a luminosity map of the area, but it depends on the level of detail you require for your qualification.

I hope this helps.


Thanks twanmul,
Meanwhile I found the European standard (EN 12464-1, 2012), where it mention this values, 500 lux - For pharmaceutical production area
750 lux- for Inspection area.