A thorough review of the literature regarding building ventilationandCO2 buildup,andtheirassociationwith health,comfort,andproductivitywasrecentlycompiled by Seppänen et al. (1999). Their review summarizes the resultsof22studiesofSBSsymptomsinofficebuildings where CO2 measurements were made over 30,000 subjectsinmorethan400buildingsinNorthAmerica,Europe, and Asia. About one-half of the studies found a statisticallysignificant(pÆ0.05)positiveassociationbetween CO2 levels and one or more SBS symptoms. In these studies, indoor CO2 concentrations were associatedwithheadache,fatigue,eyesymptoms,nasalsymptoms, respiratory tract symptoms, and total symptom scores. The respiratory symptoms included throat and lower respiratory symptoms, and difficulty breathing. Whenconsideringstudiesofmechanicallyventilatedor air-conditioned buildings but not the naturally ventilated buildings, the proportion of studies showing a statistically significant positive association between CO2 andSBSsymptomsroseto70%.Theseassociations forCO2andSBSinofficebuildingswereconsistentwith the observed association between building ventilation and SBS symptoms. When the studies are aggregated, there is a statistically significant higher prevalence of SBSsymptomsinbuildingswithventilationratesbelow10 Lsª1 compared with buildings with ventilation rates at or above 10 Lsª1. The review also indicated that severalstudiesfoundthatincreasesinventilationratesto20 Lsª1 were associated with significant decreases in SBS symptoms.