Emission Test Chambers Research Articles

Thin film models with constant source: model selection in a stochastic setting

Dunn and Tichenor [Atmospheric Environment, 22:885--894, 1988] proposed a class of differential equation models to describe the phenomenon of transient sink behaviour for organic emissions exhibited by interior surface films in state-of-the-art emission test chambers. The proposed model selection scheme embeds the derived models within a class of stochastic differential equations. The quality of model fit varies inversely with the strength of the stochastic forcing term; that is, if the model is adequate the stochastic forcing term should be small. Data from a particular application where the source can be considered to be constant demonstrates the approach. The approach can be applied to any phenomenon that is modelled by a class of linear differential equations where different models are embedded within a full model. References B. D. Anderson and J. B. Moore Optimal Filtering, Prentice--Hall, Inc., Englewood Cliffs, N. J., 1979. C. F. Ansley and R. Kohn A geometrical derivation of the fixed interval smoothing algorithm. Biometrika, 69:486--487. J. E. Dunn and B. A. Tichenor. Compensating for sink effects in emissions test chambers by mathematical modeling. Atmospheric Environment, 22:885--894, 1988. M. R. Osborne and T. Prvan. Smoothness and conditioning in generalised smoothing spline calculations. J. Austral. Math. Soc. Ser. B, 30:43--56, 1988. T. Prvan and M. R. Osborne. Model selection in a stochastic setting. ANZIAM J., 45(E) ppC787--C799, 2004. http://anziamj.austms.org.au/V45/CTAC2003/Prva/home.html H. E. Rauch, F. Tung and C. T. Striebel. Maximum Likelihood Estimates of Linear Dynamic Systems. AIAA J., 3: 1445--1450, 1965. G. Wahba. Improper priors, spline smoothing and the problem of guarding against model errors in regression. J. R. Statist. Assoc., 40:364--372, 1978. G. Wahba. A comparison of GCV and GML for choosing the smoothing parameter in the generalised spline smoothing problem. Ann. Statist., 13: 1378--1402, 1985. W. Wecker and C. F. Ansley. Signal extraction approach to non linear regression and spline smoothing. J. Amer. Statist. Assoc., 78: 81--89, 1983.

MEASUREMENT OF VOLATILE ORGANIC COMPOUNDS EMISSION FACTORS FROM COATING MATERIALS BY USE OF A THREE LITERS CHAMBER

A 20 liters chamber which is standardized in JIS A 1901:2003 “Small chamber method - Determination of the emission of volatile organic compounds and aldehydes for building products” has been popularly used for measurement of volatile organic compounds (VOC) emission factors from coating materials. A 3 liters chamber which was newly developed for measurement of VOC emission factors from coating materials was evaluated and compared with the 20 liters chamber in the study. Air tightness, recovery and mass transfer coefficient of the 3 liters chamber were evaluated in accordance with JIS A 1901:2003. Further, correlation between VOC emission factors obtained by the 20 liters chamber method and the 3 liters chamber method was examined through measurement of acrylic enamel paint and a textured coating material.The results can be summarized as follows;1) Air tightness of the 3 liters chamber meets the requirement of ENV13419-1:1999 “Building products, Determination of the emission of volatile organic compounds - Part1: Emission test chamber method.”2) Recovery and mass transfer coefficient of the 3 liters chamber satisfy the requirements of JIS A 1901:2003.3) VOC emission factors obtained show high correlation between the 20 liters chamber method and the 3 liters chamber method.

Measurement of semi-volatile organic compounds emitted from various types of indoor materials by thermal desorption test chamber method

This paper presents measurements on semi-volatile organic compounds (SVOCs) emitted from building materials, household electric appliances, and indoor products. It is extremely difficult to apply the emission test chamber method to the accurate measurement of SVOCs because they are absorbed by the internal walls of the chamber. The authors have reported on the development of the thermal desorption test chamber method that can measure correctly the emission rates of SVOCs emitted from materials under actual room-air temperature conditions. This method is composed of two measurement steps. In the first step we capture organic compounds emitted as gaseous matter. After removing the test piece from the chamber, in the second step we continuously gather the organic compounds absorbed by the chamber's internal walls while heating the chamber. We have used this method to measure emissions from various objects, and have confirmed that most SVOCs are caught in the second step. In this paper, we also report on our verification of the accuracy of SVOC measurements taken using an emission chamber and describe the emission characteristics of SVOCs.

A microscale device for measuring emissions from materials for indoor use

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 (mu-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 mu-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 mu-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 mu-CTE relative to a recovery from a 1 m(3) 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.

Reactions between ozone and building products: Impact on primary and secondary emissions

Reactions of ozone on common building products were studied in a dedicated emission test chamber system. Fourteen new and unused products were exposed to 100–160 ppb of ozone at 23 °C and 50% RH during 48 h experiments. Ozone deposition velocities calculated at steady state were between 0.003 cm s −1 (alkyd paint on polyester film) and 0.108 cm s −1 (pine wood board). All tested product showed modified emissions when exposed to ozone and secondary emissions of several aldehydes were identified. Carpets and wall coverings emitted mainly C 5–C 10 n-aldehydes, typical by-products of surface reactions. Linoleum, polystyrene tiles and pine wood boards also showed increased emissions of formaldehyde, benzaldehyde and hexanal associated with reduced emissions of unsaturated compounds suggesting the occurrence of gas-phase reactions. The ozone removal on the different tested products was primarily associated with surface reactions. The relative contribution of gas-phase reactions to the total ozone removal was estimated to be between 5% and 30% for pine wood boards depending on relative humidity (RH) and on the incoming ozone concentration and 2% for polystyrene tiles. On pine wood board, decreasing ozone deposition velocities were measured with increasing ozone concentrations and with RH increasing in the range 30–50%.

Influence of molecular parameters on the sink effect in test chambers

The determination of the specific emission rates of individual products and materials under indoor-related conditions requires the use of climate-controlled emission test chambers. However, most chambers demonstrate an inherent sink effect, i.e. the released components undergo adsorption/desorption processes with construction materials. Furthermore, this sink effect is enhanced by introducing an adsorbing sample surface into the test chamber. The degree of adsorption, as well as the extent of the recovery, can vary significantly for different chambers and samples and also depends on the physical properties of the relevant substance. Whereas the sink effect caused by the chamber itself can be reduced by using appropriate construction materials, it is not possible to avoid the sink effect attributable to the actual sample. For this reason it is of importance to evaluate chambers and samples for possible sink effects, taking into consideration the physical properties of substances. This can be achieved by kinetic modeling of emission data and determination of rate constants. The kinetic parameters obtained from curve fitting were combined with molecular parameters and applied to multivariate statistics. The properties of three different chambers with and without sink could be compared by cluster analysis. Principal component analysis revealed that the sink effect essentially depends on the boiling point of the substances examined. Emission test chambers are operated by research institutions and testing laboratories for different purposes. The determined emission rate value of a building product is a function of the chamber construction, the material to be tested and the molecular properties of the target compound. In this work it is demonstrated, which parameters have the main influence on the test result. Furthermore it is shown how multivariate statistical analysis can be applied to experimental data to characterize the sink effect under dynamic conditions. This new technique provides a suitable tool for the evaluation and comparison of test chambers.

Determination of VOC and TVOC in Air Using Thermal Desorption GC-MS – Practical Implications for Test Chamber Experiments

The determination of volatile organic compounds (VOC) species and concentrations are important for the evaluation of indoor air quality. Numerous methods exist for the determination of levels of both VOC and TVOC (total volatile organic compounds). These include the use of direct-reading instruments as well as gas chromatographic techniques. The benefits and drawbacks of the various methods are well known, and none provide precise measurement of the complex VOC mixtures that constitute TVOC in indoor air. A specific approach for TVOC measurement has been proposed in Europe in ECA-report no.19 to overcome these shortcomings. On this basis a practical analytical method was developed and applied to emission test chamber studies. Special focus was required on compounds of high volatility and the preparation of calibration standards.

Thin film models in a stochastic setting

Dunn and Tichenor (1988) proposed a class of differential equation models to describe the phenomenon of transient sink behaviour for organic emissions exhibited by interior surface films in state-of-the-art emission test chambers. Data from a particular application is used to exemplify the use of a model selection scheme which embeds the derived models within a class of stochastic differential equations. These embeddings have the property that the quality of model fit varies inversely with the strength of the stochastic forcing term. Results of this modelling application are discussed.

VOC- and SVOC-emissions from adhesives, floor coverings and complete floor structures

Emissions of volatile organic compounds (VOC) and semivolatile organic compounds (SVOC) from materials for flooring installation (primer, screed, adhesive, floor covering) were measured by means of emission test chambers and cells over a time period of at least 28 days at 23 degrees C, 50% relative humidity and an area specific air flow rate of q = 1.25 m(3)/m(2) h. Single components were tested in comparison to three complete structures (same concrete, primer, screed, adhesive) with different types of floor covering (PVC, carpet, linoleum). Sorption into concrete/screed and different permeability of flooring materials affected the emissions from the complete structures. The complete structures with linoleum and PVC showed the same types of emission and emission rates as the individual floor coverings themselves. Emissions from the carpet-covered structure resulted also from the lower layers. In all cases emissions from the complete structures were lower than the sum of emissions from the single components. For two adhesives the formation of secondary emissions (aldehydes and organic acids) was observed starting after the standard testing time of 28 days. This paper gives a survey of possible emissions of VOCs and SVOCs from flooring materials and adhesives. On the example of these materials it is shown that the determination of SVOC-emissions from materials is important because after a few weeks the emission rates for SVOCs might be higher than for VOCs. In the real indoor environment SVOCs will be probably adsorbed to dust but by means of emission test chambers or cells the determination of emission rates from materials is possible. With the knowledge of this "emission potential" it is possible to estimate also the release of SVOCs into the (indoor) environment.

Emissions of organophosphate and brominated flame retardants from selected consumer products and building materials

Abstract The emissions of selected flame retardants were measured in 1- and 0.02-m3 emission test chambers and 0.001-m3 emission test cells. Four product groups were of interest: insulating materials, assembly foam, upholstery/mattresses, and electronics equipment. The experiments were performed under constant environmental conditions (23°C, 50% RH) using a fixed sample surface area and controlled air flow rates. Tris (2-chloro-isopropyl)phosphate (TCPP) was observed to be one of the most commonly emitted organophosphate flame retardants in polyurethane foam applications. Depending on the sample type, area-specific emission rates (SERa) of TCPP varied between 20 ng m−2 h−1 and 140 μg m−2 h−1. The emissions from electronic devices were measured at 60°C to simulate operating conditions. Under these conditions, unit specific emission rates (SERu) of organophosphates were determined to be 10–85 ng unit−1 h−1. Increasing the temperature increased the emission of several flame retardants by up to a factor of 500. The results presented in this paper indicate that emissions of several brominated and organophosphate flame retardants are measurable. Polybrominated diphenylethers exhibited an SERa of between 0.2 and 6.6 ng m−2 h−1 and an SERu of between 0.6 and 14.2 ng unit−1 h−1. Because of sink effects, i.e., sorption to chamber components, the emission test chambers and cells used in this study have limited utility for substances low vapour pressures, especially the highly brominated compounds; hexabromocyclododecane had an SERa of between 0.1 and 29 ng m−2 h−1 and decabromodiphenylether was not detectable at all.

Time course of isocyanate emission from curing polyurethane adhesives

Abstract The time course of isocyanate emission from curing polyurethane (PUR) resins and adhesives was studied in two different emission test chambers. The measured emissions were strongly dependent on the type of experiment. The adhesives under investigation contained different types of diisocyanates and are used for different applications, e.g. for fixing of textile floor coverings. The influence of the curing mechanism on emission was studied by comparing the emission curves of one-component adhesives (OCA) and two-component adhesives (TCA). For TCA, the decrease in isocyanate emission was found to follow a two-step process during curing. In the first step, the emission is dominated by surface evaporation, and the decay of emission is mainly caused by the decrease in monomer content due to reaction. In the second step, the release is limited by internal diffusion. The influence of monomer reactivity on the emission profile could be demonstrated for 2,4′- and 4,4′-MDI. The less-reactive 2,4′-MDI caused prolonged emission. A strong dependence of emission rates on temperature and adhesive viscosity was also obvious. The evaluation of emission rates of different commercially available PUR adhesives showed the highest emission from systems that are applied at high temperatures. The high reactivity of diisocyanates requires special techniques for sampling and analysis. Therefore, an analytical method using HPLC–MS/MS was developed that enables limits of quantitation of

Suitability of small environmental chambers to test the emission of biocides from treated materials into the air

Abstract Biocides are used to protect materials that might be damaged by fungal, microbial or insect activity. The aim of this study is to develop a method for the measurement of these organic compounds, which generally have low or moderate vapor pressures. The biocides considered in this study are permethrin, dichlofluanid, tolylfluanid, iodpropinylbutylcarbamat, octylisothiazolinone, tebuconazole and propiconazole. The emission from two commercial products (plastic foil, wool carpet) containing biocides and of seven types of biocidal formulations applied to wood or clay tiles were investigated in 20-l glass emission test chambers. Each chamber test was performed over a period of 100–200 days, and one investigation was conducted over several years. Compared to volatile organic compounds, low-volatility compounds show totally different emission curves in chamber tests; maximal emission values may be reached in days or weeks. A period of 3 months is sometimes necessary for the determination of area-specific emission rates (SERa's). The SERa's (μg m−2 h−1) from biocide-containing products were determined for permethrin (0.006), propiconazole (0.3), dichlofluanid (2.0), tolylfluanid (1.0), octylisothiazolinone (2.5) and iodpropinylbutylcarbamat (2). In most cases, the SERa stayed at its maximum value or declined slowly over the test period. Additionally, a chamber test begun in 1994 with a piece of wood treated with a typical mixture of biocides dissolved in a technical solvent was continued. SERa's (μg m−2 h−1) for dichlofluanid (0.20), tebuconazole (0.49) and permethrin (0.08) remained detectable after the period of nearly 9 years during which the sample remained continuously in the chamber. This test proved the very slow decrease of emission of low-volatility compounds like permethrin and tebuconazole.

Flame retardants in the indoor environment - Part II: release of VOCs (triethylphosphate and halogenated degradation products) from polyurethane

Organophosphate esters, halogenated and non-halogenated, are frequently used for fire protection of building materials. With regard to toxicological profiles it is desired to avoid human exposure in the indoor environment. Moreover, some hazardous volatile organic compounds detected in indoor air are directly linked to the utilization of flame retardants. In this study, different polyurethane (PUR) products for building and indoor use treated with organophosphate flame retardants were tested in 1 m(3) emission test chambers. Emissions of flame retardants and degradation products were measured under living conditions. A PUR hard foam sample showed area-specific emission rates >100 microg/m(2) h for the compound triethylphosphate. During the tests several chlorinated degradation products of organophophorous flame retardants could be identified in the chamber air.

Formation of organic indoor air pollutants by UV-curing chemistry

UV-curable systems for manufacturing of furniture and parquet form a major and growing field in radiation curing. Numerous types and combinations of photoinitiators have been developed for crosslinking of acrylated systems and unsaturated polyesters. The properties of the photoinitiators being used in these materials must fulfill requirements like low toxicity, low odor and high reactivity. However, volatile reaction products being produced during the photochemical process contribute to the pollution of indoor air by emission from the surface and may cause strong odor and adverse health effects. Therefore, the release of photoinitiators, fragmentation products and monomers from UV-cured coatings was studied as a function of time under realistic living conditions in emission test chambers and cells. Main components detected in the chamber air were benzaldehyde, cyclohexanone, benzophenone and acrylate monomers. The area-specific emission rates SER A were found to be strongly dependent on the climatic conditions.

Isocyanate emission from PUR adhesives: influence of temperature, monomer content, and curing mechanism.

The isocyanate emission potential of polyurethane (PUR) adhesives was evaluated by measuring the area-specific emission rate (SERa;microg m(-2) h(-1)) in a laboratory emission test chamber. The chamber was constructed for the analysis of reactive substances allowing quantitative trapping of all isocyanate monomers emitted from the substrate. Isocyanates were analyzed as their 1-(2-pyridyl)piperazine derivatives by HPLC with fluorescence and UV detection. The influence of temperature, the content of the diisocyanate in the resin, and the system pressure were investigated. These parameter studies gave evidence thatthe diisocyanate emission from the resins is a gas-phase-limited mass transfer. The overall mass-transfer coefficient (beta = Ddelta(-1)) was calculated for HDI and MDI. From the temperature dependence of emission rates, the enthalpies of evaporation for 2,4'-MDI, 4,4'-MDI, and HDI from their resins were determined. The influence of monomer content on SERa followed Henry's and Raoult's laws in the cases of HDI and MDI, respectively, allowing the prediction of emission rates proportional to diisocyanate content. Therefore, from simple parameters such as application temperature and monomer content, isocyanate emission rates can be predicted. Additionally, MDI emission from curing PUR adhesives was studied. These results elucidate the influence of monomer reactivity and curing mechanism on the decrease of MDI emission with time.

Phthalic esters in the indoor environment--test chamber studies on PVC-coated wallcoverings.

Phthalic acid esters are important additives in polyvinyl chloride (PVC) products. Since PVC plastisoles for the production of wallcoverings contain about 30% phthalic acid esters, it is a crucial question whether these products can contribute to the pollution of the indoor environment. In this study, the emission of several technically relevant phthalates from PVC-coated wallcoverings were measured in emission test chambers under standard room conditions. During a 14-day test period, both the chamber air concentrations and the condensation on a cooled plate (fogging) were determined. In the chamber air, maximum concentrations of 5.1 micrograms/m3 for di-n-butylphthalate (DBP), 2.08 micrograms/m3 for di-pentylphthalate (DPP) and 0.94 microgram/m3 for di-(2-ethylhexyl)phthalate (DEHP) were found. After 14 days of exposure, up to 60.4 micrograms DEHP and 17.7 micrograms DPP could be quantified on the cooled plates of the fogging apparatus. The amounts of DBP and DIBP were significantly lower. A simple exposure calculation indicated no specific risk of an increased phthalate exposure in rooms with PVC wallcoverings.