A microscale device for measuring emissions from materials for indoor use
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Emission test chambers or cells are used to determine organic vapour emissions from construction products under controlled conditions. Polymeric car trim component emissions are typically evaluated using direct thermal desorption/extraction. The Microchamber/Thermal Extractor (μ-CTE, Markes International) was developed to provide both a complementary tool for rapid screening of volatile organic compound (VOC) emissions—suitable for industrial quality control—and a means for thermal extraction of larger, more representative samples of car trim components. To determine the degree of correlation between conventional emission test methods and the microchamber, experiments were carried out under different conditions of temperature, air change rate and sample conditioning time. Good quantitative and qualitative correlation was obtained for measurements at ambient temperature. Moreover, it was shown that ambient-temperature emissions data collected using the μ-CTE as rapidly as possible—i.e. with minimal or no sample conditioning time—nevertheless provided a reliable guide as to how well that material would perform in subsequent 3-day chamber tests of VOC emissions. The parameters found to have the greatest influence on data correlation for experiments carried out at elevated temperatures were the sample mass (for bulk emissions testing) and the conditioning time. The results also showed that, within the constraints of inherent sample homogeneity, the μ-CTE gave reproducible emissions data, despite its small sample size/capacity relative to that of conventional chambers. Preliminary results of modelling the air flow within a microchamber using computational fluid dynamics showed a high degree of turbulent flow and two potential areas of still air which could cause sink effects. However, the experimental data reported here and in previous studies showed enhanced recovery of semivolatile components from the μ-CTE relative to a recovery from a 1 m3 conventional chamber. This indicates that if these areas of relatively still air are present within the microchamber, they do not appear to be significant in practice.