Emission cells

The sensitivity of a photo-emissive cell (phototube) may be considerably increased by means of the so-called photomultiplier tube. The latter consists of an electrode covered with a photo-emissive material and a series of positively charged plates, each charged at a successively higher potential. The plates are covered with a material which emits several (2-5) electrons for each electron collected on its surface. When the electrons hit the first plate, secondary electrons are emitted in greater number than initially struck the plate, with the net result of a large amplification (up to 106) in the current output of the cell. The output of a photomultiplier tube is limited to several milliamperes, and for this reason only low incident radiant energy intensities can be employed. It can measure intensities about 200 times weaker than those measurable with an ordinary photoelectric cell and amplifier. 

Clausen, P.A., Xu, Y., Kofoed-Sorensen, V., Little, J.C. and Wolkoff P. (2007) The influence of humidity on the emission of di-(2-ethylhexyl) phthalate (DEHP) from vinyl flooring in the emission cell FLEC . Atmospheric Environment, 41, 3217-24. 

Wolkoff P. (1996) An emission cell for measurement of volafrle organic compounds emitted from building materials for indoor use-the field and laboratory emission cell FLEC. Gefahrstoffe-Reinhaltung der Luft, 56 (4), 151-7. 

Emission test cell Portable device for the determination of volatile organic compounds emitted from building products. The emission cell is placed against the surface of the test specimen, which thus becomes part of the emission cell (ISO, 2006b). 

Figure 5.2 Different types of devices for emission testing A Field and Laboratory Emission Cell (FLEC) B WKI 1 m3 glass chamber with Fast Mobility Particle Sizer (FMPS) C 1 m3 stainless steel chamber D Microchamber E WKI 48m3 stainless steel chamber.

ASTM (2005) D 7143. Standard Practice for Emission Cells for the Determination of Volatile Organic Emissions from Indoor Materials/Products, American Society for Testing and Materials, Philadelphia, PA, USA. 

Uhde, E., Borgschulte, A. and Salthammer, T. (1998) Characterization of the field and laboratory emission cell-FLEC flow field and air velocities. Atmospheric Environment, 32, 773-81. 

Wolkoff, P., Salthammer, T. and Woolfenden, E. (2005) Emission cells and comparison to small chambers for materials emission testing. Gefahrstojfe-Reinhaltung der Lufi, 65, 93-8. 

Standard practice for emission cells for the determination of VOCs from indoor materials/products... 

Air distribution Air velocity is never completely uniform across the sample surface Though surface air velocity does vary in emission cells as in chambers, cells do preclude the variability of sample orientation... 

The fundamental difference between test chambers and cells is that samples are placed within test chambers whereas test cells are placed onto the emitting surface of a product or material. Emissions cells are limited to planar materials or applied paints /coatings and cannot be used for moulded or nonplanar materials. However, they are inherently quicker and easier to use than chambers and eliminate the... 

The determination of the emission versus time behavior under living conditions can be modeled by the use of test chambers or emission cells (see Chapter 6). 

Jensen, B., Wolkoff, P., Wilkins, C.K. and Clausen, P.A. (1993) Characterisation of linoleum. Part 1 measurement of volatile organic compounds by use of the field and laboratory emission cell, FLEC. Proceedings of Indoor Air 93, Vol. 2, pp. 444-7. 

Medium-resolution absorption spectrometer emission spectrometer with red-sensitive photomultiplier or CCD detector laser excitation source such as listed in Table 1 (or medium pressure mercury arc such as described in earlier editions of this text) neon calibration lamp and power supply (available from, e.g.. Oriel Corp., Stratford, CT) reagent-grade iodine 100-mm glass cell with Teflon stoppers for absorption studies heating tape with controlling Variac 50-mm cell for emission studies vacuum system, preferably with a diffusion pump and cold trap, for pumping down emission cell. 

The field and laboratory emission cell affords a portable, nondestructive method of testing the surfaces of potential VOC sources. In addition to its utility as a climatic chamber, it provides valuable information on source strength, which can be used for source apportionment and to formulate strategies for emission control. Wolkoff et al. [85] used it to identify emission processes in a number of building materials, while Jarnstrom and Saarela [66] recently utilised it to show that the dominant source of 2,2,4-trimethyl-l,3-pentadiol-diisobutyrate in the indoor air of some problem apartments was the floor surface. 

Apart from the field and laboratory emission cell, other instruments that have been used for source identification and apportionment include... 

Fig. 4 Field and laboratory emission cell - top view (Photo T. Salthammer)...

Table 3 Quality requirements for emission test chamber and emission cell according to EN 13419-1 [12] and EN 13419-2 [33]. TVOC represents total volatile organic compound ...

Parameter Emission test chamber Emission cell... 

As another method of examination for the tasks listed above, the so-called emission test cell, e.g. the FLEC (field laboratory emission cell see Chapter 2.2) can be employed to determine surface emissions. 

The field and laboratory emission cell (FLEC) is a microchamber designed for emission testing of volatile organic compounds (VOCs) from, e.g., building materials. In contrast to traditional climate chambers, in the FLEC and other emission cells the test material becomes part of the cell itself. 

Emission cells such as the FLEC may be useful in many applications, e.g. for routine testing in manufacturers product development and production control. 

Ekbeig L.E., Gunnarsen L., Knutti R., Haas J. and Mogl S. (1995) Identification of air pollution sources in office buildings using the Field and Laboratory Emission Cell. Proceedings of Healthy Buildings 95, Milan, Italy, Vol. 3, 1353-1358. 

Gustafsson H., Jonsson B. and Lundgren B. (1995) Chemical emission from paints and other surface materials-measurements with Field and Laboratory Emission Cell (FLEC) and other climate chambers. In Bagda E. (ed) Emissionen aus Beschichtungsstoffen, Chapter 8, Stand der Technik, Analyse der Emissionen und deren Einfluss auf die Innenraumluft, 95-105. Expert Verlag. 

Roache N.F., Guo Z., Fortman R., and Tichenor B.A. (1996) Comparing the Field and Laboratory Emission Cell (FLEC) with traditional emissions testing chambers. Characterizing sources of indoor air pollution and related sink effects. ASTM STP 1287, Tichenor B. (ed) American Society for Testing and Materials, 98-111. 

Uhde E., Borgschulte A. and Salthammer T. (1997) Characterization of the Field and Laboratory Emission Cell (FLEC) Impact of Air Velocities on VOC Emission Rates. Proceedings of Healthy Buildings/ lAQ 97, Washington DC, Vol. 3, 503-508. 

Wolkoff P., Clausen P.A., Nielsen P.A., Gustafsson H., Jonsson B., Rasmusen E. (1991) Field and Laboratory Emission Cell (FLEC), Conf. Proceedings of Healthy Buildings 91, Washington D.C., USA, Sept 4-8, 160-165. 

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