This report describes tracer gas measurements of the local mean age of air at different locations within an office room. These results are used to assess the distribution of fresh air atdifferent depths, and to give guidance on the depth over which single-sided ventilation is effective.
The passive perfluorocarbon method (PFT-method) has been successfully applied in ventilation measurements in rooms. The method is, in principle, also applicable to air flow measurements in ventilation ducts. There are, however, several problems in applying a passive sampling technique in a duct. First, the concentration of the tracer may not be uniform through the cross-section of a duct. Second, the velocities in a duct are normally an order of magnitude higher than in a room.
Tracer gas tests were conducted on a five-storey apartment building to determine the air and contaminant flow patterns within the building. The test method involves the injection of a small amount of tracer gas, SF6, into a selected location to create a single source and monitoring the tracer gas concentrations at locations throughout the building. Based on the rates at which the tracer gas concentrations change at various locations, the air and contaminant flow patterns within the building can be determined. Several such tests were conducted.
Ten years ago the automated constant concentration tracer gas (CCTG) method was conceived at the Technological Institute, Tastrup, Denmark. This technique is now used by researchers toexamine a wide variety of air infiltration and ventilation related problems. At this juncture it would seem appropriate to summarise the development of the CCTG system and examine its use in present day research.
This paper describes the extension of the previously described UMIST technique for the determination of airflows between two interconnected cells to the case of three connected cells, and gives the results obtained for a series of validation experiments carried out under controlled conditions.
Local and room mean ages of the air in a room may be measured by three versions of the tracer gas technique; which are the pulse method, the tracer step-up up method and the tracer decay method. The values of mean age obtained are of course subject to errors in the measurement of the tracer gas concentrations. The sensitivity of the three methods to errors in the tracer gas concentration is not the same, and in some cases can be very large. In order to examine this problem, test measuremenb have been carried out in a model room using the three difEerent methods.
This paper discusses three methods for measuring interzonal air movements in two zone buildings: 1. initial injection of one tracer into a single room, 2. repeated injection of one tracer in two rooms, 3. initial injection of two tracers in two rooms. The description of these methods includes an outline of the theoretical background, the presentation of suitable injection strategies and algorithms for the evaluation of the concentration profiles.