Lighting installations with higher intensity and tuneable white light may increase production output, and reduce fatigue, errors and accidents.
The effects above are bigger - or at least easier to document - for repetitive tasks. Higher intensity in combination with the right light colour spectrum and careful timing of the various lighting settings may lead to higher alertness and among industrial workers. The result is less fatigue, which again leads to fewer errors being made. For shift workers, light may be used to phase-shift the daily rhythm, to ease the adaptation to night work.
For the dayshift in production environments an activating light in the morning should be switched on for 1-2 hours, starting 1-2 hours after the shifts begin to allow night owls to reach the right position on their bodily performance curve. The cool white light shifts the daily rhythm forward. A too early exposure may lead to a phase delay.
|Day shift settings. The cool white light is switched on at 9 am, 2 hours after shift start. A cool white shower in the afternoon mitigates the post-lunch slump in bodily performance. Cylindrical illuminance Ez at 1,2 m to the right, colour temperature to the left.|
Night shift lighting requires careful consideration of the wanted effect. In the case of few night shifts (2-3 nights) in a row the worker does not want to shift his or her sleep pattern, but keep the day cycle. Hence light sources with a low circadian activating effect must be used at night. To increase alertness and reduce the risk of errors at the end of the night shift, we recommend an exposure to cool white light the last hours of the night shift. This could be combined with individually controlled cool white light “showers” every hour during the second half of the shift.
|Light cycle for night shifts without phase shift. The neutral white light lasts until the last couple of hours where a cool white activating light increases workers’ alertness and concentration. |
If the night shift cycle goes on for more than 3-4 nights in a row, a temporary shift of circadian rhythm is wanted. That means a phase delay of ca 8 hours so that the worker is awake at night and sleeps directly after the night shift. He or she wakes up again in the afternoon.
It will take at least 4-5 days to shift circadian cycles like this1
. In this case we recommend light sources with a high circadian activating effect early in the night shift, with a shift of exposure timing backwards for each shift, until the worker has changes his or her daily rhythm sufficiently.
|Light setting for the night shift, day 1. A cool white light for the first 3-4 hours of the shift shifts the daily cycle backwards. On shift day 2, the activating light is switched on one hour later at 20.00 and lasts until midnight. This goes on until the backward 8 hour circadian shift is complete.|
1 M. Gibbsa,b, S. Hamptona, L. Morganb, J. Arendta, 2002. Adaptation of the circadian rhythm of 6-sulphatoxymelatonin to a shift schedule of seven nights followed by seven days in offshore oil installation workers.