Air quality measurements along with airflow rate measurements of air-conditioning system were conducted in an office building occupied by workers with clerical activities. Contaminants measured were C0₂, SPM (suspended particulate matters), NOx and airborne bacteria.

Indoor C0₂ and SPM levels were found to be quite high, 1,600 ppm (C0₂) and 0.25 mg/m³ (SPM), respectively, at their maximum and exceeded Japanese Standards.

The cause of the high concentration was found to be airleakage in the outdoor air intake duct. The airleakage rate was estimated applying mass-balance model of CO₂. Results indicated that the actual outdoor air intake rate was less than half of that expected. The applicability of the model was examined and it was considered to be practically satisfactory.

Units: SI