Indoor Carbon Dioxide Concentrations and SBS in Office Workers

Relationships between indoor carbon dioxide (CO₂) levels and mucous membrane and lower respiratory sick building syndrome (SBS) symptoms are explored in 41 office buildings from the US EPA BASE study. Elevated indoor CO₂ concentrations may indicate inadequate ventilation per occupant and elevated indoor pollutant concentrations, leading to SBS symptoms. Two CO₂ metrics were constructed: average workday indoor minus average outdoor CO₂ (dCO₂, range 6-418 ppm), and maximum indoor one-hour moving average CO₂ minus outdoor CO₂ concentrations (dCO₂MAX). Multivariate logistic regressions quantified dCO₂/SBS symptom associations, adjusting for personal and environmental factors. A dose-response relationship (p<0.05) with odds ratios per 100 ppm dCO₂ ranging from 1.2 to 1.5 for sore throat, nose/sinus, tight chest, and wheezing was observed. The dCO₂MAX/SBS regression results were similar. Implications: large increases in ventilation rate or improvements in ventilation effectiveness and/or indoor pollutant source control would be expected to decrease the prevalence of selected symptoms by up to 70-85%.