Abstract:
This study was to investigate sources and concentrations of volatile organic compounds (VOCs) and air exchange rates (AER) in 17 office buildings in Bangkok, Thailand. Sampling was conducted during September-October 2009. Personal sampling pumps were used to draw air at a flow rate 0.04 min⁻¹ through Tenax-TA⁻¹ sorbent tubes. The cartridges incorporated ozone scrubbers to prevent VOCs losses on the sorbent surface. Air sampling was taken during 10:00-12.00 am and 1:00-3:00 pm on a weekday. At each sampling site, three categories of samples were collected, i.e., two indoor samples and one outdoor sample. Samples were then analyzed using thermal desorption (TD) and a gas chromatrography/mass spectrometer (GC/MS). Measurement of the office air exchange rates was performed by a constant injection technique using hexafluorobenzene as a tracer gas. Thirteen target VOCs were investigated including benzene, toluene, m/p-xylene, o-xylene, styrene, ethylbenzene, hexane, chloroform, 1,2-dicholroethane trichloroethylene, 1,2-dichloropropane, tetrachloro ethylene and limonene. Results showed that the levels of indoor and outdoor toluene were the highest valve (110.19 and 43.61 µg./m².), and followed by limonene, m/p-xylene, ethylbenzene, and o-xylene. Teh mean concentrations were 73.53, 12.20, 12.09 and 9.63 microgram/cubic meter, respectively. The air exchange rates ranged from 0.017 to 1.16 hr⁻¹. Ninety-four percent of the measured office had the air exchange rate below 0.67 hr⁻¹. (Building Control Act B.E. 2522 (A.D. 1979)). Furthermore, indoor/outdoor (I/O ratios) of the target compounds ranged from 1.68 to 12.29. This indicated that indoor sources are significant contributors to the level of indoor VOCs in comparison to the outdoor source