Type of ventilation system in office buildings and sick building syndrome.

To examine the role of types of building ventilation in office buildings as a determinant of ocular, nasopharyngeal, skin, and general symptoms often denoted as the sick building syndrome, a cross-sectional study was carried out in March 1991 on 2,678 workers from 41 office buildings selected randomly from the Helsinki metropolitan area. The ventilation type and other characteristics of these buildings were recorded on a site visit, and a questionnaire directed to workers inquired about the symptoms, perceived air quality, and possible personal and environmental determinants (response rate, 81%). The outcomes were weekly work-related symptoms experienced during the previous 12 months and symptom groups defined either by their anatomic location or hypothesized mechanism. In logistic regression analysis adjusting for potential confounders, simple mechanical ventilation (mechanical supply and exhaust ducts) was related to a higher risk of ocular symptoms (odds ratio (OR) = 1.31, 95% confidence interval (CI) 0.76-2.26), nasal congestion (OR = 1.78, 95% CI 0.92-3.42) and discharge (OR = 1.44, 95% CI 0.72-2.88), pharyngeal symptoms (OR = 2.32, 95% CI 1.01-5.33), and lethargy (OR = 1.71, 95% CI 0.99-2.95) compared with natural ventilation. Air conditioning was related to a slightly higher risk of symptoms compared with simple mechanical ventilation (for any symptom, OR = 1.30, 95% CI 1.00-1.68). Steam and evaporative humidification as well as air recirculation acted also as determinants of these symptoms. The risk of the studied symptoms is related to the type of ventilation in the existing office building stock. Future studies should explore the typical functional problems and specific causes connected with the high-risk ventilation systems.