Ventilation of buildings is important for occupants' health. Few studies have been conducted on associations between home ventilation and occupant's health in China. During 2013-2016, we measured air change rate in 98 homes by both mass balance of occupant generated CO2 method and PFT method in Tianjin and Cangzhou, China. Questionnaires were used to survey the health data for children. We found that air change rates measured by CO2 method in whole day were higher than those measured by PFT method and those measured during night. Lower air change rates measured by CO2 method during night were significantly associated with perceived unpleasant odor (p=0.04). Lower levels of air change rate measured by CO2 method during night were risk factors for croup (AOR: 7.30(1.25, 42.60)). Air change rate measured in a certain period especially at night may be more representative in analysis of the association with occupants' health.