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The effects of mechanical ventilation on the sick building syndrome were evaluated in an office building with 2150 employees. The ventilation rate was known to be high in the building. The main hypothesis put forward was that reducing the rate of mechanical ventilation would alleviate symptoms. A short-term trial was carried out by shutting off the ventilation in one part of the building, reducing it in two areas and leaving one part unalteredas a control. The reduction of ventilation had, if any, an opposite effect to that anticipated. There was a linear correlation between increase in symptoms and rise in room temperature to above 22°C.
Many complaints about drafts occurred even though the measured average velocities were only 0.05 m/s. Ventilation rates per person varied greatly depending on the location in the building and on the number of persons in a room. The variation of the temperature between the rooms was large. Tobacco smoke bothered people although smoking was not allowed in the offices.
In the analysis of the data many confounding variables were found. Women expressed their symptoms almost twice as often as men. The age, allergic disposition, and overall job satisfaction had also a significant effect on the symptoms. These factors were controlled in the analysis.
Based on the study, temperature seems to be the most important variable in indoor climate and it should be individually controlled.
sick building syndrome, office building, ventilation rates, room temperature, draft, air-conditioning system
Professor of Mechanical Engineering, Faculty of Helsinki University of Technology,
Unit of Statistics, National Public Health Institute,