In a week that saw a judge throw out of civil court a women's claim for damages against Ronnie Scott's jazz club in London after she drunkenly fell down the stairs, Lux's technical editor, Alan Tulla asks, what do you need to do to check that your staircase meets the regulatory requirements?
In the UK, the Health and Safety Executive’s Guide HSG38 'Lighting at Work', published in 1997, gives minimum recommended illumination levels that meet health and safety requirements. Inside this document, it states that these recommendations should provide the minimum light levels necessary for the health and safety of employees. They apply to interior and exterior lighting intended for everyday use.
The average illuminance required in HSG38 is 20 lux and the minimum measured illuminance required is five lux. It has a footnote that states that only safety has been considered because no perception of detail is needed and visual fatigue is unlikely. Where there are other considerations, which might need to be taken in to account, the HSG recommends referring to the CIBSE/SLL Code for Lighting.
The levels recommended in the Code for Lighting are based on the European Standard EN12464-1, 2011 which is published in the UK as BS EN 12464-1. For indoor stairs, escalators and travellators, the recommendation is for an average illuminance of 100 lux. It also requires that there is 'enhanced contrast on the steps'.
The main reason for the difference between these values and those of the HSG document is that EN 12464 concerns performing the given visual task efficiently and accurately, rather than the minimum required for safety. Here, the task is walking up and down a staircase.
One omission is that the recommendations are an average over an undefined area; although one would reasonably assume that it would be the horizontal illumination on the stair treads including the most important top and bottom ones.
There is an important exception to these requirements and this applies to dim environments where the standard 100 lux level may be distracting or cause problems with visual adaption. As well as night clubs and bars, hospitals often have dim lighting at night to allow for the observation of patients. Museums and art galleries sometimes have sensitive objects illuminated to only 50 lux and their surroundings are much darker.
The general principle in dim environments is that the top and bottom step of any flight of stairs are illuminated more brightly than their immediate surroundings. They should also have a contrasting nosing on each step.
To give a perceptual difference, the first step should be lit to a lighting level one 'standard lighting interval' above ambient. These lighting intervals are in the Code for Lighting and taken from EN 12665. The lower levels are 20 – 30 – 50 – 75 – 100 – 200 lux. As an example, if the average illuminance on the floor is 20 lux, the first step should be 30 lux.
The Society of Light and Lighting will shortly be issuing a guidance document on the specific issue of lighting for stairs.