We estimated decreasing rate of indoor air pollutants with are airborne bacteria, airborne fungi, formaldehyde, total volatile organic compounds, PM10, and PM2.5 in 10 children’s hospitals and 6 childbirth houses located in Seoul and Gyeonggi-do from November to December in 2012. Sectional period was respectively divided for operating and non-operating the air cleaners. There was a trend that concentration of surveyed pollutants in children’s hospitals and childbirth houses during operating period decreased among indoor air. We used Monte-Calro simulation to remove uncertainty and identify efficiency of eliminated pollutants such as surveyed pollutants by the air cleaners. Average efficiency of removal were 61.39±21.42% for airborne bacteria, 71.77±19.65% for airborne fungi, 73.37±24.62% for formaldehyde, 71.20±25.96% for total volatile organic compounds, 65.16±23.80% for PM10, and 71.06±23.97% for PM2.5. Keywords : Air cleaners, Airborne bacteria, Airborne fungi, Indoor air, Air pollutants