Low Ventilation Rates
In a review of the literature (LBNL-43334), almost all studies found that ventilation rates below 10 Ls^-1 per person in all building types were associated with statistically significant worsening in one or more health outcomes.

With Lower Ventilation Rates

• 20 of 27 studies found statistically significant increase in symptoms
• 9 studies found >80% increase in prevalence of at least one symptom
   

Figure 2. The Potential Benefits of 5 L/s per person increase in Ventilation Rates Most Common SBS symptoms decreased by ~40%

High CO₂ Concentrations
In an analysis (LBNL-51570) of the 100 buildings of the US EPA Building Assessment Survey and Evaluation (BASE), statistically significant associations of mucous membrane and lower respiratory SBS symptoms were found with increasing CO₂concentrations.

Figure 3. Dose response relationship between binned dCO2 and MM and LResp symptoms in 100 BASE study buildings. ORs and 95% CIs shown are the results of adjusted models including covariates listed in Table 6 and the SUSCEPT variable. DCO2 bins reflect the 10th and 90th percentiles of the dCO2 distribution, and three bins evenly split between them. P-values shown reflect the fit of the dose-response model with smaller p-values indicating a better fit. (LBNL-51570)

Air Conditioning
Relative to natural ventilation, air conditioning, with or without humidification, was consistently associated with a statistically significant increase in the prevalence of one or more SBS symptoms. Prevalences were typically higher by approximately 30% to 200% in the air conditioned buildings. (LBNL-47457) (LBNL-50046)

Figure 4. Comparison of SBS Symptoms with Natural Ventilation and AC (Seppanen and Fisk, in press)

High Indoor temperature
Temperatures greater than the optimum temperature of the comfort zone has been associated with greater SBS symptom severity.(LBNL-48217)
 

Figure 5. Relationship of Temperature With SBS Symptom Severity in NIOSH/LBNL Healthy Building Intervention Study (Mendell et al., in press)

High VOC Concentrations
In a study of the 100 buildings of the US EPA Building Assessment Survey and Evaluation (BASE), it was found that VOC sources were observed to play a role in direct association with mucous membrane and lower respiratory irritation, and possibly to be indirectly involved in indoor chemical reactions with ozone that produce irritating compounds associated with SBS symptoms. (LBNL-51570)
 

Figure 6. Health Effects of Pollutant Mixtures: Association of New VOC Metrics with SBS Symptoms (EPA BASE Study and California Healthy Building Study)

HVAC contamination
 

Figure 7. Association of HVAC Risk Factors with Building-Related Lower Respiratory Symptoms (Source)