Mechanical Ventilation in Office Buildings and the Sick Building Syndrome. An Experimental and Epidemiological Study

Abstract

The effects of mechanical ventilation on the sick building syndrome (SBS) were studied in an office building with 2150 employees, where the mechanical ventilation and indoor air quality were commonly blamed for causing symptoms typical of the SBS (nasal, eye, and mucous membrane symptoms, lethargy, skin symptoms and headache). The mechanical ventilation rates in the building were high (mean 26 l/s/person). To test the hypothesis that mechanical ventilation causes the SBS, a controlled experimental study was carried out by shutting off the ventilation in one part of the building and reducing the ventilation rate by 75% and 60% in two areas while leaving one part unaltered as a control. The experimental reduction of the ventilation rate did not alleviate the symptoms. On the contrary, the reduction of the ventilation rate caused a slight but statistically significant relative increase in symptoms (p < 0.05). In the cross-sectional analysis of the baseline data the SBS symptoms did not associate significantly with the ventilation rate (range 7–70 l/s/person). In the linear regression model, a positive correlation was found between temperatures above 22°C and the occurrence of symptoms (p < 0.05). Subjects exposed to environmental tobacco smoke had more symptoms than those not exposed (p < 0.01). Women reported more symptoms than men (p < 0.001). In addition, any prior history of allergic diseases (p < 0.001) and a negative attitude towards the social atmosphere at work (p < 0.001) were significant determinants of the SBS.