Temporal and spatial variations in IAQ and its association with building characteristics and human activities in tropical and subtropical areas

A repeated measurement was conducted for the purpose of examining the seasonal and spatial variations in indoor air quality (IAQ) in tropical and subtropical areas as well as comparing the differences between different climate areas. Indoor and outdoor temperature, relative humidity (RH), formaldehyde (HCHO), CO₂, bacteria, and fungi were measured in tropical and subtropical areas for four seasons from 2012 to 2015 for eight households. Questionnaires were conducted during each visit for the purpose of determining the factors influencing the IAQ. Considerable seasonal and spatial differences were observed in indoor HCHO and CO₂ concentrations. The results of the study indicated that although the trends of indoor and outdoor CO₂, HCHO, bacteria, and fungi concentrations and ratios were similar in the different climate areas, the levels were higher in tropical and subtropical areas than in other climate areas. In the tropical and subtropical areas, the levels of indoor and outdoor temperatures and RH were similar, and the values were higher indoors than outdoors in cold or temperate areas. In addition, a regression model indicated that residential building and human activities affect the levels of indoor environmental pollutants in tropical and subtropical areas. In summary, variations in indoor air pollutant level differed in different climate areas. Therefore, it is necessary to study the management of residential characteristics and human activities to improve the IAQ in tropical and subtropical areas.