| Summary: | 碩士 === 國立臺灣大學 === 環境工程學研究所 === 89 === We set up an environmental testing chamber system accroding to the standard test methods of U.S. ASTM D5116-97. Both particleboard and medium-density fiberboard（MDF） were selected to investigate the relationship between emission factor of formaldehyde and environment parameters, including temperature, relative humidity, and air exchange rate.
In the experiment testing how the humidity affects the emission factor of formaldehyde of 10mm-thickness composite boards. When the relative humidity is at 50%RH, the concentration of formaldehyde is between 150μg/m3 to 250μg/m3 and 20μg/m3 to 80μg/m3 for particleboard and MDF. As relative humidity increases to 80%RH, the concentration increases to 250μg/m3 to 500μg/m3 and 80μg/m3 to 180μg/m3. The increase in concentration is due to the moisture in the air which reacts with urea-formaldehyde resins at the surface of the board. The increase also agrees with the increase in emission factor range of formaldehyde from 300-500μg/m2/hr and 50-150μg/m2/hr to 500-1000μg/m2/hr and 200-400μg/m2/hr for particleboard and MDF, respectively.
Formaldehyde would gain extra energy which make itself easier to escape from the samples when temperature rises from 15°C to 30°C. The concentration of formaldehyde increases from 150-250μg/m3 to 350-475μg/m3. Therefore, the emission factor also increases from 300-500μg/m2/hr to 700-900μg/m2/hr. Under the same condition, the results from MDF experiments showed that it has more improvement in formaldehyde emission under the influence of temperature. At for MDF, the concentration of formaldehyde rises from 25-75μg/m3 to 200-450μg/m3, and the emission factor increases from 50-150μg/m2/hr to 500-900μg/m2/hr.
At high air exchange rate（about 2ACH）, the concentration of formaldehyde in the environment chamber is diluted with inlet gas. Therefore the concentration of formaldehyde at higher air exchange rate is lower than the lower one. At high air exchange rate, the concentration of formaldehyde from MDF is diluted from 25-80μg/m3 to 20-60μg/m3. But the gradient of formaldehyde at surface would increase and more formaldehyde escapes from MDF. That is the reason why the emission factor at high air exchange rate is greater than that of lower air exchange rate. The quantity of emission factor is 50-160μg/m2/hr and 100-200μg/m2/hr.
Compared with the 10mm-thickness boards, the 18mm-thickness boards emit more formaldehyde. This is because thicker boards are made of more resins which results in more emissions. 18mm-thick boards emit about 2 times formaldehyde than 10mm-thick boards do. The particleboard we selected emits more formaldehyde than MDF. Therefore, our results suggest that the low formaldehyde MDF board did have lower formaldehyde emission, although it still emit much formaldehyde at high temperature.
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