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This issue is sponsored by the Philips Romania, Lighting Division

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INFLUENCE OF THE COLOUR TEMPERATURE OF THE<br />

PREFERRED LIGHTING LEVEL IN AN INDUSTRIAL WORK AREA<br />

DEVOID OF DAYLIGHT<br />

Henri JUSLÉN<br />

<strong>Philips</strong> <strong>Lighting</strong>, Finland<br />

The first objective of <strong>the</strong> study was to find out if preset colour temperature and illuminance<br />

level affects <strong>the</strong> preferred lighting levels in an industrial work environment. The second<br />

objective was to measure if <strong>the</strong> illuminance or colour temperature has an effect on<br />

productivity. A dimmable task-lighting system was installed above eight individual<br />

industrial assembly workstations. Four preset “switch-on” settings were employed (4400<br />

K/350 lux, 4400 K/820 lux, 3500 K/350 lux, 3500 K/820 lux). The system allowed <strong>the</strong><br />

workers to change <strong>the</strong> illuminance but not <strong>the</strong> colour temperature using IR-controllers<br />

after <strong>the</strong> lighting was switched on. The values selected <strong>by</strong> <strong>the</strong> (regular) workers were<br />

recorded. It was found that slightly lower task-lighting illuminances were selected when<br />

<strong>the</strong> colour temperature was higher, and a much higher illuminance was selected when <strong>the</strong><br />

preset switch-on illuminance was higher. The productivity of <strong>the</strong> workers was significantly<br />

higher (5.7 per cent) when <strong>the</strong> higher colour temperature was in use. The switch-on<br />

illuminance did not affect productivity.<br />

Keywords: lighting, productivity, colour temperature, preferred illuminances.<br />

1 Introduction<br />

In most cases, lighting <strong>is</strong> designed to meet <strong>the</strong><br />

minimum norms and up until now most of <strong>the</strong><br />

lighting research has neglected to study <strong>the</strong><br />

lighting preferences of industrial workers. It<br />

<strong>is</strong> worthwhile to build up knowledge with<br />

respect to <strong>the</strong> preferences of workers<br />

regarding lighting level and light colour and<br />

to establ<strong>is</strong>h whe<strong>the</strong>r <strong>the</strong>re are any differences<br />

between workers. <strong>Th<strong>is</strong></strong> information could<br />

help to create lighting conditions that workers<br />

prefer, thus increasing <strong>the</strong>ir well-being and<br />

indirectly influencing productivity.<br />

INGINERIA ILUMINATULUI 18-2006<br />

Inside Europe <strong>the</strong>re are differences<br />

between <strong>the</strong> colour temperatures preferred.<br />

More lamps with a warmer colour<br />

temperature are sold in nor<strong>the</strong>rn Europe and<br />

more lamps with a cooler colour<br />

temperature in <strong>the</strong> south. <strong>Th<strong>is</strong></strong> <strong>is</strong> typically<br />

explained <strong>by</strong> <strong>the</strong> differences in wea<strong>the</strong>r and<br />

temperature conditions. In areas with a lot<br />

of daylight, <strong>the</strong> colour temperature of <strong>the</strong><br />

artificial lighting <strong>is</strong> not so evident because<br />

of <strong>the</strong> contribution of <strong>the</strong> daylight. In<br />

office-lighting studies, where people’s<br />

control behaviour has been studied<br />

(Maniccia et al. 1999; Escuyer and

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