Indoor pollutants seem to have a negative affect on people from vulnerable households who are considered to be weak by the department of environmental health, such as the elderly, infants, children, patients, and pregnant women. In this study, the concentrations of pollutants were measured, especially those pollutants that endanger vulnerable households such as PM10, HCHO, TVOCs, TBC and fungi. The measurements were taken from September to October of 2013 in the Chungnam area. The results were as follows: PM10 33.2 μg/m3, HCHO 20.35 μg/m3, VOCs 132.30 μg/m3, TBC 562.71 CFU/m3 and fungi 362.04 CFU/m3. In the case of TBC and fungi, there were excessive concentrations at 30.9% and 49.3% compared to the standards set by WHO. In the case of fungi, buildings built before the 1980s showed a concentration of 446.23 CFU/m3, those built in the 1980s and 1990s had a concentration of 320.21 CFU/m3 and those built in the 2000s had a concentration of 313.43 CFU/ m3 indicating that fungi concentration was higher when the building was older. The correlation analysis between indoor air pollutants and factors affecting indoor concentrations indicate that HCHO (r = 0.423), TVOCs (r = 0.329), and humidity (r = 0.359) showed a significant difference (p < 0.01). The current study focused on vulnerable households that were unable to protect themselves from indoor pollutants and where poor living circumstances prevailed such as households that do not receive much sunlight; thus, more attention and focus needs to be given to these particular households. Keywords : VOCs, HCHO, Indoor air, TBC