Indoor air quality can be affected by indoor sources, ventilation, decay and outdoor levels. Understanding the effectiveness of indoor air quality control depends on knowledge of the characteristics of air pollutants in indoor air, especially their quantities and persistence, and the relevance of indoor sources to these factors. Toluene within new and established houses has been determined and factors significant to its presence have been identified. A total of 30 selected houses in Seoul, Asan and Daegu areas that were constructed within 4 years and over 4 years of construction were measured the concentration of toluene from July to September in 2004. Toluene emission decay of double-exponential model exhibited good fit of $Y=276.37e^{-1.21x}(R^{2}=0.34,;P=0.06)$ for 2 years and then $Y=51.54e^{-0.11x}(R^{2}=0.40,;P=0.0)$ from 23 years in new houses. In case of living in new houses, noncarcinogenic health effects of exposure to toluene was 1.38 of hazard quotient (HQ) comparing to toluene reference dose of 0.13 mg/kg-day.