Abstract
The health risk from exposure to indoor air pollution is greater than from outdoor. To effectively promote indoor air quality control, the EPA has issued the draft of the Indoor Air Quality Control Act in 2005 and set the recommended value of indoor formaldehyde concentration as 0.1ppmv. The standard method for determining formaldehyde in air required the sample being brought back to laboratory for analysis and used several ml of chloroform per sample. We replaced the liquid-liquid extraction used in current standard method by solvent bar microextraction. The approach successfully prevented waste generation and reduced organic solvent use, fulfilling the principles of green chemistry. We also used a portable formaldehyde detecting instrument equipped with an 2,4-dinitrophenyl hydrazine (DNPH) –coated filter, which could determine formaldehyde concentration on-site in 10 min. We compared the analytical performance between the standard method and the portable method by determining the indoor formaldehyde concentrations in three newly renovated home/office/shops which used many wooden products. The values ranged from 0.133~0.321 ppmv and were all above the recommended values. The relative percent difference were all smaller than 20%，In one location, the formaldehyde concentration decreased from 0.279 ppmv to 0.131 ppmv after 30 min ventilation。The findings demonstrate the compatibility between these two methods and effective reduction of indoor formaldehyde could be achieved by sound ventilation. We also used TiO2 photocatalyst to degrade formaldehyde. The results show that TiO2 photocatalyst prepared by layer-by-layer method saved time, good uniformity, and high light transmission, which could achieve degradation efficiency of 90%. TiO2 could effectively degrade aldehydes (C1~C5). Low carbon aldehydes showed better efficiency. The aldehyde was converted to carboxylic acid first, then to aldehyde with lower carbon number. The rate of the later reaction (decomposition) is smaller than the former one (oxidization).