A change in "Lux" lighting, how significant are the differences?

[Donna]

Hi, Just wondered it there was anyone out there that is "Genned up" on the difference between one set of Lux readings to the next, basically a before and after scenario,

I have in my possession 2 floor plan maps of the same building, the first has numbered corridors and a lux reading in each corridor,

I have also some comments by the owner of the building to state the lighting was changed, but it was hardly significant!
I would dearly love someones factual advice on the readings,  The readings were taken with a light Meter.

I will list the before and after readings applying to each numbered corridor and stairways.

                          Before                               After
Corridor 1
(Base of stairs)       40                                   97

Stairway                20                                 187

Corridor 2             20                                  430

Corridor 3             40                                  121

Corridor 4  
(Long corridor)  20  40  20                           160
(brightest in the middle
due to one bulb)              


Based on the fact that this is a public building, can I ask, Were the first readings Legal?

[Chris Houston]

This isn't a fire safety issue.

Lighting requirements in UK workplaces are all covered by the Workplace (Health, Safety and Welfare) Regulations 1992.

Since the Health & Safety at Work Act 1974, the law stop being prescriptive on this.  What is required is for is "suitable and sufficient" lighting - there is no obligation to provide natural lighting.

The thing to note is that the term "suitable and sufficient" is used generally throughout the regs must be decided certainly with reference to the task and also to an extent the person: so what is suitable for someone just needing to use computers, is not necessarily suitable for threading needles, or fixing watch mechanisms.

Clearly also, people need to move about safely.

And also what is adequate for one person is not necessarily adequate for another - there is also an obligation on the employer to maintain, so that a flickering fluorescent is clearly a problem.

[John Webb]

Hi! Can I presume this is the public building you were asking for advice on a while back?

The new figures certainly show a considerable improvement on the old. But as to whether the old were illegal or not, we need to consider what Building Regs were in place at the time either the building was erected or when the lighting was last changed. Or if indeed the Regs actually required minimum light levels at the time.

I designed and installed new lighting at my local 1825 church about 8 years ago. Refering back to my notes at that time I have got from somewhere not recorded:
Movement areas: 50 to 100 lux at floor level
General areas where reading etc takes place: 100 lux minimum, 300 lux preferable, at the table or other level at which reading takes place.

It would be worth looking at the older BRs in your local reference library, if they have them.
A look at the CIBSE website might yield some useful information on lighting as well. (Sorry, can't remember what their web-site is.)

Be interesting to know what levels the emergency lighting reaches when the main lights are out!

[Donna]

Thankyou to both of you, John I will check out the website,
 Chris, I forgot to mention that a piece of machinery is was used in the 20 lux area, and that this corridor was partially blocked with Chairs and tables, (I know that bit is a fire safety issue) but sadly no-one checked this for 3 months after Fire service were informed!
I am nor sure how quick the fire service should investigate after it being brought to their attention.

[jokar]

Donna, the HSE publish a gudiance note HSG 38 on artificial lighting levels to go alongside BS 5266 parts 1, 7  and 8 which is about Emergency and Emergency Escape Lighting EEL).  HSG 38 provides information on supposed lighting levels for normal use dependent on premises categorisation.  The Guidance Note is available from the HSE website as a free download.  As a by the by EEL levels are 0.2, 1 and 5 lux, whilst normal lighting levesl for an office environment are 200 lux.

[Donna]

Cheers Jokar,
Ive seen the guidance notes, but as a lay person, I wanted to know if I had good cause to challenge someones statement who quoted "Yes the lighting was slightly upgraded, but this was an un significant change"

[John Webb]

The changes in light levels are, by any reasonable standard, significant to very significant.
40 to 97 = approx a 2.5 times increase
40 to 160 = a 4 times increase
20 to 430 = an enormous 22 times increase (approx).

Hope that helps.

[kurnal]

John do you know if lux is a linear scale and what difference would it make in terms of  human perception of lighting levels? This  posting is of relevance to escape route illumination rather than task lighting?

[jokar]

1 lux is one candle power ie the light from a lit candle.  Most mobile phones nowadays give off 1 lux when the torch is on.

[John Webb]

"Lux" is a linear scale - ie a figure if doubled means there is twice as much light per unit area.

I don't have a copy of the BS etc on escape route lighting, only excerpts. As I recall the lighting levels are typically about a 1/100 of those needed to use the premises. Sorry for the imprecision!

[wormhole]

There are very few statutory requirements for lighting levels, CIBSE http://www.cibse.org(Chartered Institute of Building Services Engineers) produce several lighting guides including the 'Code for Interior Lighting' this gives guidance on appropriate lighting levels for various types of building and room. note that figures quoted are from my memory of the CIBSE guide, and these figures are average illuminance with a uniformity of around 0.7 (although this can vary depending on the type of area) - also note the CIBSE guides are non-statutory.

Basically, the requirements on illuminance are based on what level of detail is required to be seen, normally around 100-150lux for circulation spaces, 300 lux for reading, 500 lux for detailed work up to 1000 lux for traditional drawing offices.

Because the human eye is extremely good at adjusting to different lighting levels, you can be reasonably flexible with applying this guidance.

Although the first set of readings were below the guides, as the are point readings its difficult to assess fully, as all the guides work on average illuminance levels.

There is nothing to say legal or not though.

Obviously emergency lighting is a different matter - normally its 1 lux for escape routes (or 0.2 if ALWAYS unobstructed), 0.5 lux for open areas over 60m2 and 10% of normal lighting level or 15 lux for high risk areas.

the 0.2 lux equates to a night with a full moon, which most people can get around in OK (once the eyes have adjusted) which is where the 0.2 lux comes from.

Lighting and emergency lighting design is much more complicated than this, but it should give you an idea!