Environmental test chamber concentrations

Abstract Adsorption and desorption of indoor air pollutants to and from indoor surfaces are important phenomena. Often called sink effects, these processes can have a major impact on the concentration of pollutants in indoor environments and on the exposure of human occupants to indoor air pollutants, Basic theories are used to describe the processes using fundamental equations. These equations lead to models describing sink effects in indoor environments. Experimental studies have been performed to determine the important parameters of the sink models. Studies conducted in dynamic, flow-through environmental test chambers have quantified adsorption and desorption rates for many combinations of indoor air pollutants and interior surfaces. Sink effects have been incorporated into indoor air quality (lAQ) models to predict how adsorption and desorption processes affect... 

Chamber measurement Supply air quality Background concentration Sink effects/recovery Air exchange ratio Air tightness of the environmental test chamber Internal air mixing Air velocity Accuracy of temperature, RH and air exehange ratio Product loading factor... 

The accuracy of any model to predict VOC concentrations in test chamber experiments mostly depends on the accuracy of the source (term ER in Eq. 1) and sink submodels (terms A and D in Eq. 1) incorporated into the lAQ model. In other words, a realistic estimate of human exposure to VOCs emitted from indoor materials and products requires knowledge not only of their emission rates but also of their adsorption/ desorption capacity or the buffer effect on VOC concentrations in indoor air. Small environmental test chambers are increasingly used in order to characterize the emission of VOCs (i.e. the source term in Eq. 1) from materials and products present indoors, whether they are used to realize the building environment, maintenance work (includ-... 

Long-term respiratory exposures are usually patterned to projected industrial experience, giving the animal a daily exposure 6 hours after equilibrium of chamber concentrations, for 5 days a week (intermittent exposure) or 22 to 24 hours of environmental exposure per day, 7 days a week (continuous exposure), with 1 hour for feeding and maintaining the chambers. In both the cases, the animals are usually exposed to a fixed concentration of test materials. A major difference to consider between intermittent and continuous exposure is that in the former there is a period of 17 to 18 hours in which animals may recover from the effects of daily exposure, and an even longer recovery period during weekends. 

After analytical test methodology, board orientation within the chamber, positive vs negative air displacement for make-up air to the chamber, air make-up measurements, and environmental controls were all evaluated and standardized, it became apparent to chamber operators that board preconditioning was a very important factor in obtaining comparable chamber results on identical board samples. Tables VI-A VI-B provide data on laboratories A and B chamber round-robin before and after proper conditioning facilities and procedures were standardized. As can be seen in Table VI-A, the relationship of chamber concentrations between Lab A and Lab B on matched board sets before preconditioning procedures were established varied between 25 to 67%. After preconditioning procedures were established and carefully followed, the variation of chamber concentrations between Lab A and Lab B dramatically improved over five fold for matched board sets, i.e. 0 to 13.5% as shown in Table VI-B. 

A small 3 cm x 3.5 cm section of the catalyst-coated desiccant wheel (25 cm diameter) was cut and placed in specially made holder shown in Fig. 12.9-6a. The piece of sample was tested in a 0.2 m3 environmental chamber at Chiaphua Industries Ltd. (Fig. 12.9-6b) for reduction of airborne VOC. The chamber was filled with the target VOCs through two stage saturators shown in Fig. 32b. Once the VOC level in the chamber stabilized, the fan was turned on to circulate the air through the sample. Three sets of sensors were located at the inlet and outlet of the holder, as well as in the center of the chamber. The chamber temperature and relative humidity were kept constant during the test. Figure 12.9-6c shows the results for VOC levels of 4000, 2000 and 1000 ppb at room temperature. The reduction rate was slower because of the low VOC concentration and the poor air circulation in the chamber. Also unlike the Prototype Unit, the catalyst was kept at room temperature throughout the test. 

Carboxyhemoglobin Concentration [HbCO] This can be estimated with the method of Jones and co workers. The subject holds a deep breath for 20 s to allow equilibration of carbon monoxide between alveolar air and blood and then expires a sample of that air into a container. The air carbon monoxide concentration may be directly related to carboxyhemoglobin concentration [HbCO]. The test can be performed before exposure in an environmental chamber to help to verify that the subject has not received inordinate ambient pollutant exposure. 

Monitoring and Evaluation. Program model Simpson, 1995), predictions are 27% higher than the mean whereas the lowest, the CB4-TNO version of the carbon bond 4 mechanism, predicts ozone concentrations 35% below the mean. Other studies in which the carbon bond 4 mechanism was tested against environmental chamber data have also found that it underpredicts 03 formation (e.g., Simonaitis et al., 1997). The sensitivity of predicted 03 by CB4 to the chemistry, particularly radical-radical reactions, has been discussed by Kasibhatla et al. (1997). 

In this paper, all the blends and composites are designated by the type of matrix (G for the neat nylon, D for the 8 wt % rubber-modified nylon and N for the 20 wt % rubber-modified nylon), the concentration of fibres and the type of fibre/matrix interface (A or B). As an example, a material designed DlOB is a ternary blend made of DZ matrix and 10 wt% of type B fibres. After drying the specimens for 24 hours at 100°C, they were stored in plastic bags inside a desiccator. In comparison with freshly injection moulded samples, the moisture content in the specimens ready for mechanical testing is about 2 wt%. All the mechanical tests were conducted in an environmental chamber in controlled conditions a temperature of 20°C under a continuous argon flow. 

Although the entire MCM has been tested in atmospheric models, and through intercomparison with the results of chamber-validated mechanisms (e.g. Derwent et al, 1998 Jenkin et al, 2002), it has only been partially tested using environmental chamber data. It has been used in a number of studies involving die European Photoreactor (EUPHORE) in Valencia (EUPHORE, 2002), providing the basis for validation of the mechanisms for selected VOC. MCM v3 chemistry has thus already been tested for the photo-oxidation of a-pinene-NOx mixtures at comparatively low NOx concentrations (Saunders et al, 2003). The aromatic mechanisms in MCM v3 and MCM v3.1 have also been evaluated against a set of smog-chamber experiments the evaluation was focused on four representative species of the... 

The test platform was comprised of a refuge chamber (Figure 1) with an internal net volume of 6.84 m, an air purifier (24V, 30 W) as shown in Figure 2, and a KJ70 coal-mine safe-production monitoring system, which is used to monitor concentrations of such environmental parameters as 2, CO, COj, CH4, HjS, temperature, and relative humidity inside in real time. 

SO2 would be of great environmental benefit. The process can be accomplished in the electrode chambers of cells divided by a cation-exchange membrane and filled with circulating 3 M sulfuric acid solution. In tests, current densities of up to 2 A/cm were realized at 60°C. With platinum catalysts it was possible to attain up to a 90% conversion of SO2, even when its concentration in the gas stream to the anode was low (see the review of Alcaide et al., 2006). 

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