Test chambers wall concentration

Center of the U.S. Bureau of Mines. The radon chamber in Denver Research Center is designed to provide adjustable humidities and a well controlled, monitored radon and CN concentration. It has a length of 213 cm, a diameter of 152 cm, and a volume of about 3.89 m. The walls are made of 0.5-cm rolled steel with welded seams. Figure 1 shows the general scheme of the test chamber excluding the transducers and data aquisition system. 

A sink effect is the fact that the released components partially adsorb within the test chamber, for example, at the chamber walls (Sollinger, Levsen and Wiinsch, 1993). This can result in an incorrect reading of the concentration determined at the chamber outlet, which can lead to the wrong emission rate being computed. 

Emission ofDEHP from PVC wall coverings (containing 30%phthalic esters) was measured in a test chamber at room temperature, maximum concentration of 0.94 g/m3 for DEHP in air over 14-day test period (Udhe et al. 2001). Other citations within this reference noted that DEHP in test chambers was not detectable at room temperature, but maximum concentrations of 5.2 and 2 g/m3 were measured at 60 and 40 °C, respectively. Increases in DEHP emissions with increasing ambient temperature are especially... 

By means of chamber tests in combination with an appropriate sampling and desorption method it is possible to get information about the emission behavior of wood preservative agents out of treated wood or generally of biocides emitted from other materials. In spite of the sink effects determined it is possible to calculate emission rates if an equilibrium between air and wall concentration is reached. Furthermore, it is possible to get information about sink effects if certain materials are Introduced into the chamber and analyzed afterwards or the biocide concentration on the chamber walls is determined. From this data, in combination with the knowledge of the amount of biocides used for treatment, relative losses by emissions can be calculated. 

Highest concentrations of contaminants including plasticizers in air were reported for test chambers built to identify and quantify emissions from products used indoors. In test chamber studies evaluating the emission of phthalates from PVC coated wall coverings maximum concentrations of 5.1 pg/m (= 5,100 ng/m ) for DBP, of 0.50 pg/m for DiBP and of 0.94 pg/m for DEHP were observed in a 14 day test period (Uhde et Organophosphates (TBP, TBEP, TCEP, TCPP, TDCPP, TEHP, TPP) used for car interior components and evaluated in emission test chambers led to the highest concentrations for TPP of about 2 pg/m (= 2,000 ng/m ). ... 

Another method (not standardised), which was used in the PICADA (Hiotocatalylic Innovative Coverings Applications for De-poUution Assessment) project [31, p. 69], consists of a testing chamber with a certain surface of photocatalytic materials at the walls of this chamber. The photoconversion of NO is looked at over time. The percentage is referred to an initial concentration of 100%. hi the case of cementitious materials as base materials, a concentration decrease is observed even without lumination, most probably due to adsorption by the hydroxides present in the cement matrix. However, the removal of NO by the action of the photocatalyst/ cementitious mahix composite is clearly much higher than the removal obtained with the photocatalyst alone or with any other combination, in the dark or in the light. Thus, once more, a synergistic effect is obtained. 

All the components of the chamber that are in direct contact with the inlet and outlet air and the chamber atmosphere have to be constructed in such a way that they emit no relevant amounts of VOC under test conditions and show only a very small sink effect (see 2.1.3.2). Suitable materials for the walls of a chamber are electro-polished stainless steel and glass. Seals are especially critical components. As little of their surface as possible should come into contact with the chamber atmosphere. Additional appliances such as fans are also problematical. The TVOC background concentration should be lower than 10 pg/m the background concentration of single compounds should be lower than 2 pg/m. ... 

---