| Summary: | 碩士 === 元智大學 === 機械工程學系 === 90 === An investigation of time budgets has found that individuals spent about 95% of their day indoors; thus, indoor air quality has played an important role on human health. Generally, indoor air pollutants can be classified into three groups, including particulate, gaseous and biological. Volatile organic compounds (VOCs) emitted by indoor materials are predominant in gaseous pollutants. The paint has been widely used inside buildings for years. After the activity of painting, indoor TVOCs concentration may be hundreds to thousands of milligram per cubic meter. In view of the fact that the half-lives of most VOCs are long, indoor exposures will produce more adverse human effects. Therefore, the objectives of this study are intended to shed light on the effects of temperature and air exchange rate (ACH) on the characteristics of TVOCs emitted from the paint, and further to establish a characteristic equation of decay coefficient (k).
Refer to the guideline of ASTM D5116-97, this study designs a small-scale environmental chamber of 53 L to simulate the indoor environment. The performance of the environmental chamber is evaluated in terms of the environmental parameters, such as temperature, relative humidity, air exchange rate, wind speed and mixing level. One solvent-based and one water-based paints widely used in Taiwan are selected, and the emission from them are sampled using the headspace method and analyzed by GC/MS. The substrate is the zinced steel for eliminating the inner diffusion. The film thick of the sample is also measured. At the relative humidity of 55% and the experimental period of eight hours, four temperatures and four air exchange rates are considered in the environmental chamber testing. The variation of TVOCs concentration with time is recorded using a direct-reading instrument, once per five minutes. In addition, the source emission models published in literature are collected, and the curve-fitting are evaluated using the experimental data.
The results show that the performance of the small-scale environmental chamber made in this study is certified. The emission analysis significantly distinguishes the solvent-based paint from the water-based. The peak value of the emission in each case almost happens at 5 minutes after the experiment starts. At the relative humidity of 55 %, the maximum peak concentration of TVOCs emanated from the paint occurs at temperature of 35℃ and air exchange rate of 1.25 hr-1, 84.1 ppm for the solvent-based and 2.3 ppm for the water-based. On the other hand, the least produces at temperature of 20℃ and air exchange rate of 2.07 hr-1, 28.3 ppm for the solvent-based and 1.0 ppm for the water-based. Generally, the peak level and emission factor rise as the temperature increases; on the contrary, the peak level and emission factor decrease as the air exchange rate increases. The result of curve-fitting suggests that the first-order decay model is better than the latex paint model for the data modeling in this study. And a characteristic equation of decay coefficient (k) is successfully established. To sum up, temperature and relative humidity are crucial parameters on TVOCs emission indoors.
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