Formaldehyde concentration and its influencing factors in residential homes after decoration at Hangzhou, China

Air pollution surveys of formaldehyde (HCHO) were conducted in 2324 rooms decorated within one year in 2007-2009 in Hangzhou, China. The mean HCHO concentration (C_HCHO) was 0.107±0.095 mg/m³, and 38.9% of samples exceeded the Chinese National Standard GB 50325-2010. Over the past 3 years, the C_HCHO decreased with time (p<0.05). Relationships of potential factors to indoor C_HCHO were also evaluated. C_HCHO was related to temperature (T), relative humidity (RH), time duration of the windows and doors being closed before sampling (DC), time duration from the end of decoration to sampling (DR) and source characteristics (d). A model to relate indoor C_HCHO to these five factors (T, RH, DC, DR, d) was established based on 298 samples (R²=0.87). Various factors contributed to C_HCHO in the following order: T, 43.7%; d, 31.0%; DC, 10.2%; DR, 8.0%; RH, 7.0%; specifically, meteorological conditions (i.e., RH plus T) accounted for 50.7%. The coefficient of T and RH, R_TH, was proposed to describe their combined influence on HCHO emission, which also had a linear relationship (R²=0.9387) with HCHO release in a simulation chamber test. In addition, experiments confirm that it is a synergistic action as T and RH accelerate the release of HCHO, and that is a significant factor influencing indoor HCHO pollution. These achievements could lead to reference values of measures for the efficient reduction of indoor HCHO pollution.