Determination of VOC Emissions from Surface Coatings by Environmental Test Chamber Measurements

Abstract: The emitting properties of different building materials are obtained by measurements in environmental chambers of a few established designs. In order to interpret the results from the measurements and to predict the influence on the indoor environment, it is necessary to have a good understanding of the parameters governing the emission process. The aim of this thesis is to contribute to this understanding by focusing on the process of emission of chemicals from building materials and on the influence of a number of parameters governing the process.

In emission studies reported in the literature, few investigations deal with the comparison of the VOC emission rates obtained by measurements in different test chambers. In the present study, a 1m³-chamber, a CLIMPAQ and a FLEC were used for measurement of the concentrations of various compounds from surface coatings. The study focuses on parameters which could be considered to have a substantial influence on the emission rates, or which do not appear to have been thoroughly studied previously. Interest has mainly been focused on the influence of air velocity, airflow rate and sorption on the emission rate, when other parameters have been maintained constant.

It was found that during the first 24 hours, by varying the airflow rate under given test conditions in a test chamber, a number of physical parameters have a direct influence on the emission process. From the start of the test until steady state has been reached, the measured concentration variations may be divided into three different phases. The results from measurements showed that the higher the airflow rates, the faster a steady state was attained. Furthermore, all the selected substances did not reach steady state at the same time during the experiments.

The effect of the air velocity above the surface on the emission of VOCs was studied in the three mentioned environmental chambers. It was found that the emission rates of the compounds at 22, 23 and 24 hours after the start of the test systematically increase with increasing air velocity. It was possible to determine the magnitude of increase to 10-20%. However, it was difficult to determine the exact level of increase of the emission rate, due to the uncertainty of the measurements and the low levels of increase.

Finally, the characterisation of adsorption of VOCs on the inside of the empty chambers has been studied. The experimental studies for all three chambers show that the sorption of substances in the 1 m³-chamber was slightly lower than in the FLEC. The CLIMPAQ shows a larger capacity of sorption with material specimens than without material specimens. This indicates that the gases emitted from painted plates adsorb again onto the test materials.