Employees' perception of lighting conditions in manufacturing plants: associations with illuminance measurements.

BACKGROUND: The aims of this study were to evaluate the employees' subjective assessments of different aspects of lighting condition as well as task area illuminance in manufacturing plants.

METHODS: This field study was conducted between March and May 2013, in three packing plants (Saveh, central Iran). Data were collected by questionnaire and measurement of the task area illuminance levels. Data were analysed using contingency coefficient test, Spearman's correlation analysis and non-parametric Friedman tests.

RESULTS: The recommended illuminance levels were not met in 46.9% of the work areas. This finding was in agreement with the employees' perception of light level, and with low satisfaction with lighting in the work environment. Adverse effects of lighting condition on job performance, changing posture for better viewing of the work area and eye tiredness were reported as 64%, 33% and 31% of the employees, respectively. Satisfaction with lighting was negatively correlated with the age of respondents (r=-0.229; P<0.010). The employees' satisfaction with lighting was also highly correlated with the employees' subjective assessments of the light level (r=0.779; P<0.001), type of artificial light sources (r=0.591; P<0.001), light colour (r=0.50; P<0.001) and use of daylight (r=0.254; P<0.004). The type of artificial light sources was correlated with job performance (r=0.311, P<0.001) and eye tiredness (r=0.273; P<0.002).

CONCLUSIONS: The findings highlight the potential usefulness of subjective assessments to supplement objective measures and provide a more holistic approach to lighting design and planning.