Associations between type of ventilation and air flow rates in office buildings and the risk of SBS-symptoms among occupants

Abstract

The association between type of ventilation and outdoor-air flow rates and Sick Building Syndrome (SBS) and SBS symptoms was studied in a cross-sectional questionnaire and field study comprising 160 office buildings, and 260–2649 respondents with case-controls as well as prevalence comparisons. Measured ventilation rates were higher than required by most building codes and consisted of fresh-air (outdoor-air) inflow of 17±14 L/p and 2.0±1.3 air changes/h. Increased risk of SBS and elevated prevalence of general SBS symptoms were associated with low outdoor-air flow rates, presence of copying machines in office rooms, and ventilation operating hours was less than 10 h/d. There was a suspected association between SBS and air humidification, recirculation of exhaust air at high outdoor-air flow rates but not at low outdoor-air flow rates, and with natural or mechanical exhaust ventilation systems. SBS was not associated with the presence of a rotary heat exchanger or with the supply air temperature higher than the room air temperature.