Indoor air quality in substandard housing in Hong Kong

Sub-divided unit (SDU) provides substandard housing in Hong Kong by partitioning a small flat into several tiny units. With typical floor area of merely 9.3 m(2), they often lack a partitioned kitchen. About 210,000 persons (2.9% of Hong Kong's population) are living in 92,700 SDUs. Inserting extra partitions significantly suppress ventilation which was pushed below building standards to degrade indoor air quality (IAQ). This study monitored the concentrations of CO, CO2, PM10, PM2.5 and VOCs in eight typical SDUs for 48 h. The mean concentrations were 367 mu g/m(3), 1216 mg/m(3), 22 mu g/m(3), 14 mu g/m(3) and 794 mu g/m(3) respectively. PM10 and VOC concentrations exceeded Hong Kong IAQ objectives (excellent class) by 1.10 and 3.89 times respectively. Indoor and outdoor CO, PM10 and PM2.5 concentrations had no significant correlation. Cooking and air conditioning use notably controlled IAQ. During open-plan cooking, spread of fumes pushed maximum PM10 and PM2.5 concentrations to exceed 1000 and 500 mu g/m(3) respectively to threaten the health of occupants especially children. CO2 and VOCs rapidly accumulated during AC use, reaching over 3000 mg/m(3) and 2000 mu g/m(3) respectively. Timely interventions are needed to reduce impacts on tenant's health and provide healthy affordable housing to low-income families.