###### Abstract  
High concentrations of air pollutants and increased morbidity and mortality rates are found in industrial areas, especially for the susceptible group, children; however, most studies use atmospheric dispersion modeling to estimate household air pollutants. Therefore, the aim of this study was to assess the indoor air quality, e.g., CO, CO2, NO2, SO2, O3, particulate matter with aerodynamic diameter less than 2.5 (PM2.5), and their influence factors in children's homes in an industrial city. Children in the \"general school\", \"traffic school\", and \"industrial school\" were randomly and proportionally selected. Air pollutants were sampled for 24 h in the living rooms and on the balcony of their houses and questionnaires of time-microenvironment-activity-diary were recorded. The indoor CO concentration of the traffic area was significantly higher than that of the industrial area and the general area. In regard to the effects of window opening, household NO2 and PM2.5 concentrations during window opening periods were significantly higher than of the reference periods. For the influence of cooking, indoor CO2, NO2, and PM2.5 levels during the cooking periods were significantly higher than that of the reference periods. The indoor air quality of children in industrial cities were affected by residential areas and household activities.  
Keywords:indoor air quality; children's house; industrial city; window opening; cooking +
Footnote †: journal:  
matter with aerodynamic diameter less than 10 and 2.5 \(\upmu\)m (PM\({}_{10}\) and PM\({}_{2.5}\)), sulfur dioxide (SO\({}_{2}\)), nitrogen dioxide (NO\({}_{2}\)), volatile organic compounds (VOCs), etc. in industrial areas may increase the risk of respiratory symptoms, and attacks of asthma in children [1; 5; 6]. Therefore, indoor air quality of children's homes may be very important to children's health, especially in industrial cities, since children spend most of their time at home [7].  
Indoor air quality may be affected by indoor human activities such as cooking, smoking, cleaning, etc. and the infiltration of outdoor pollutants produced from the traffic or industrial sources [8; 9; 10; 11]. For example, SO\({}_{2}\), NO\({}_{x}\), PM\({}_{2.5}\), and carbon monoxide (CO), the major conventional air pollutant in steel plants, oil refineries, and vehicular exhaust emissions [12; 13; 14], may enter a house through cracks and windows [15; 16]. In addition, if the indoor air is not well ventilated, the air pollutants may accumulate in the indoor environment, and then seriously affects the health of the inhabitants [17].  
Previously, atmospheric dispersion modeling was used to estimate the household concentrations of indoor air pollutants in industrial areas [1; 18; 19]. Only a few studies actually measured individual exposure [20] and household concentrations [21; 22; 23], and these studies only focused on PM mass concentrations, elemental composition, and VOCs concentrations. However, other air pollutants e.g., CO, carbon dioxide (CO\({}_{2}\)), NO\({}_{2}\), SO\({}_{2}\), and ozone (O\({}_{3}\)) in households in industrial cities also need to be considered. Therefore, the main aim of this study was to assess the indoor air quality including CO, CO\({}_{2}\), NO\({}_{2}\), SO\({}_{2}\), O\({}_{3}\), and PM\({}_{2.5}\), temperature and relative humidity, and their influence factors (e.g., window opening and cooking) in children's homes in an industrial city--Kaohsiung City. To our knowledge, this is the first study to assess the indoor air quality including CO, CO\({}_{2}\), NO\({}_{2}\), SO\({}_{2}\), and O\({}_{3}\) in children's homes in an industrial city. In addition, the second aim was to evaluate potential determinants of indoor air pollutants levels of occupants' activities, including cooking and window opening, etc. It is also the first study to reveal the differences of air pollutants between cooking periods/window opening periods and reference periods through a time-microenvironment-activity-diary via a questionnaire in one-hour time segments.