ASSOCIATIONS BETWEEN TYPE OF VENTILATION AND AIR-FLOW RATES IN OFFICEBUILDINGS AND THE RISK OF SBS-SYMPTOMS AMONG OCCUPANTS

The association between type of ventilation and outdoor-air flow rates and Sick Building Syndrome (SBS) and SBS symptoms was studied in a cr oss-sectional questionnaire and field study comprising 160 office buil dings, and 260-2649 respondents with case-controls as well as prevalen ce comparisons. Measured ventilation rates were higher than required b y 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 l ow outdoor-air flow rates, presence of copying machines in office room s, and ventilation operating hours was less than 10 h/d. There was a s uspected 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 sys tems. SBS was not associated with the presence of a rotary heat exchan ger or with the supply air temperature higher than the room air temper ature.