As control of indoor microbial contamination has become an increasing concern around the world, feasibility and effectiveness of adopting ventilation approach has attracted a significant interest. This field investigation demonstrated, quantitatively, critical variables to be taken into consideration while applying such a measure, including the kinds of microbes to be removed and the types of ventilation system already in place.

Our study conducts a series of investigations in five office buildings chosen according to the types of construction, ventilation, and building age. Formaldehyde was measured by continuous photoacoustic Multi-Gas monitor Type 1302 (Brüel & Kjaer). The 8-h average concentrations in working hours were used to estimate the lifetime cancer probability (LCP) and chronic non-carcinogenic hazard index (HI). The carcinogenic effect of formaldehyde estimate by LCP (70 years old) is about 2.06 x 10(-4) to 1.75 x 10(-3) after adjusting their working time. The levels of risk are 100-1000 times of the acceptable carcinogenic risk. A similar trend is observed for the levels of HI calculated. Many studies have suggested that exposure to high levels of formaldehyde may cause nasal cancer and other health effects. Therefore, promoting the labeling system for low emission materials to protect consumers from exposure to excessive emissions and helping the industry to develop low emission materials is evidently urgent and deserves greater efforts.