for PM 2.5 and PM 1 were higher than 0.8 for any pair of indoor and outdoor locations for all three periods, which indicates that the indoor exposure level to fine particulate matter was dominated by outdoor pollution. The SCC values for PM 10 ranged from 0.4 to 0.8 between indoor and outdoor concentrations in winter andsummer. PM 10 can be generated during indoor activities, such as cleaning and construction, which may affect the contribution from indoor sources and thus the correlations with outdoor PM 10 . Significant moderate to high correlations were observed be- tween indoor and outdoor CO concentrations, with SCC values