Comparison of Models used to Estimate Parameters of Organic Emissions from Materials Tested in Small Environmental Chambers

Two models, one physical and the other empirical, have been applied to the characterization of emission data of thin film products tested in small environmental chambers and have been compared in temts of emission results and m e of use. The physical model, being based on equations with coefficients bearing a physical meaning, is, in principle, more informative than the empirical one. However, it is uncertain whether it always gives accurate and unambiguous results. Moreover, in orakr to be exploited in a reasonable amount of time, it requires the use of non-linear regression routines, e.g. those fom SAS Institute Inc., implemented on mainframes and, even then, it is often quite diffiult to handle. The empirical model does not rely explicitly on physical effects. Although by definition it can only describe but not interpret the experimental data, it does estimate parameters describing the emission with an accuracy comparable to that of the physical model. It is easier to handle than the latter as it can employ non-linear regression routines such as those used on personal computers.     

Impact of Early Stage Incomplete Mixing on Estimating VOC Emissions in Small Test Chambers

Abstract Most of the existing emission models developed from small-scale chamber tests assume complete mixing in the chamber throughout the test period. This paper examined this assumption using a Computational Fluid Dynamics (CFD) model. The model simulated the three-dimensional air velocity profiles and Volatile Organic Compound (VOC) concentration distributions from wood stain in a well-designed mixing chamber of 1.0X0.8X0.5 m³. The model used measured data to determine the time-dependent VOC surface concentrations of wood stain. The CFD results show that the VOC concentrations in the test chamber were not uniform in the early stage (about 18 minutes). The first-order decay model using the complete mixing assumption will underestimate the Total VOC (TVOC) emission rates by 65% and 59% in the first 3 minutes and next 15 minutes, respectively. Since wood stain emitted about one third of the VOCs in the first 18 minutes, the impact of incomplete mixing in the early period is significant for calculating the material emissions. Furthermore, the mass transfer coefficient of TVOC calculated by CFD is also compared with that calculated by analogue theory and that calculated by experimental correlation.     

Application of a novel reference material in an international round robin test on material emissions testing

Emission testing of products is currently a rapidly increasing field of measurement activity. Labeling procedures for construction products are based on such emission test chamber measurements, and hence, measurement performance should be verified. One possible route is to conduct testing of one material in different laboratories within a round robin test (RRT), ideally using homogeneous reference materials, which can be used within interlaboratory studies or as part of the quality management system to ensure comparable results. The applicability of a lacquer system with nine added VOCs (hexanal, styrene, n‐decane, limonene, 2‐ethyl‐1‐hexanol, N‐methyl‐α‐pyrrolidone, 2‐ethylhexyl acrylate, dimethyl phthalate, and n‐hexadecane) was evaluated in an international RRT with 55 participating laboratories. An intralaboratory quality check confirmed the homogeneity and reproducibility of the lacquer material for most of the compounds (RSD 5%‐6%), which was confirmed in the RRT. However, emissions varied for the polar compound N‐methyl‐α‐pyrrolidone and the higher boiling compounds 1,2‐dimethyl phthalate, and n‐hexadecane which could be traced back to analytical issues. In the RRT, the interlaboratory relative standard deviations (RSDs) ranged from 30% to 65% for all participants but for reference laboratories the range was between 20% and 45%.