Infiltration of ambient PM_2.5 through building envelope in apartment housing units in Korea

Air pollution due to PM_2.5 is of public concern in Korea. Ambient PM_2.5 can penetrate indoors through the building envelope, affecting the indoor PM_2.5 concentrations. Most people stay indoors for approximately 80% of every day, implying that their primary exposure to PM_2.5 could be determined by the indoor air. This study aims to investigate the infiltration of ambient PM_2.5 through the building envelop in apartment housing units in Korea. The on-site infiltration test method, by using a blower-door depressurization procedure, was suggested in order to maintain an identical indooroutdoor pressure difference among the tests. On-site experiments were conducted in 11 apartment housing units to estimate the PM_2.5 infiltration factors. The results showed that the average infiltration factor of all the test housing units was 0.65 ± 0.13 (average ± standard deviation), with a minimum of 0.38 and a maximum of 0.88. Furthermore, the results from the relation of the building airtightness data to the infiltration factors suggests that a leaky housing unit with high ACH₅₀, or a high specific effective leakage area (ELA), would be more significantly influenced by the ambient PM_2.5. The study demonstrated that the suggested infiltration test procedure was useful to assess the infiltration factors in conditions of controlled indoor-outdoor pressure differences in real housing units.