Total suspended particle (TSP) and particulate matter (PM10 and PM2.5) were measured at 35 office buildings in Thailand. This study aimed (1) to characterize the concentrations of TSP, PM10, and PM2.5 in office buildings, (2) to determine health risk indexes, and (3) to investigate the predictive equations for PM2.5. Particle air sampling equipment and a selfadministered questionnaire were used as the tools. Average concentrations of TSP, PM10, and PM2.5 were found at 52.0±15.5, 44.3±12.2, and 31.3±10.4 μg/m3 , respectively. Health risk assessments regarding exposure to PM10 and PM2.5 were at moderate health hazard levels. A multiple linear regression model was used to create the predictive equation. The results verified that PM2.5 concentration could be well estimated under known PM10 and TSP with the r2 value of 0.88. These findings could help provide the possibility to estimate a non-monitoring value in terms of the available data.
