Modeling and controlling indoor formaldehyde concentrations in apartments: On-site investigation in all climate zones of China

Formaldehyde has substantial adverse impacts on human health, and formaldehyde exposure primarily occurs in indoor environments. This study investigated the infiltration rates and indoor formaldehyde concentrations in 5 climate zones of China. In the winter, apartments in northern China suffer from higher indoor formaldehyde concentrations than apartments in southern China. The median indoor formaldehyde concentrations were 56 μg/m3 (25%, 75%: 38, 91 μg/m3) in northern China and 40 μg/m3 (25%, 75%: 30, 61 μg/m3) in southern China. There is a clear decrease in indoor formaldehyde concentrations in China. We also studied the relationships of the indoor air temperature, years of decoration, infiltration rate and source characteristic with formaldehyde concentrations in closed conditions. A multiple regression model that related these factors to the formaldehyde concentrations in closed conditions was constructed (R2=0.75). The optimal curve for the suitable combination of temperature and infiltration rate to maintain low formaldehyde concentrations with the lowest cost was calculated for northern and southern China. By comparing the optimal curve and the state point of each city, we can infer the suitable tendency of indoor temperature and infiltration rate for each city. In Tianjin and Shenyang, apartments are overheating, thus causing a high percentage of some homes to have formaldehyde concentrations above the Chinese national standard. In Shanxi, Xinjiang, Yunnan and the Yangtze River Delta, the infiltration rate should be increased to some extent to achieve better indoor air quality. In Hunan, Hubei and Chongqing, indoor temperatures could be increased to improve indoor thermal comfort.