The study characterised the mixing of tracer gas in three ventilation systems with two different airflow rates (totally outdoor air).The test procedure is presented and errors are calculated and compared.
Five different techniques of tracer gas measurement are reviewed in order to determine the total ventilation airflow rate as well as air distribution in the room, on site or in laboratory. Examples of applications are given insisting on the two most recent techniques.
This paper is based upon the results of measuring and simulating the air change in the single apartment of 5-storey multi-family dwelling. The technique of tracer gas concentration decay was applied to be able to assess the rate of air change. The building was used as normal by occupants so the results should be very accurate. The main aim of the research was to validate simulation methods used to predict infiltration. Multiven -the authors own program - was used to achieve this aim.
Describes a project which attempted to match simulated and measured tracer gas test results and to determine how much effort is necessary to produce sufficiently accurate results. The research assessed the overall value of CONTAM96 as a representative example of available simulation-model programs from both technical and practical viewpoints.
States that it is difficult to achieve good mixing in a large space and that the usual methods to evaluate the ventilation system in such large spaces with the age of air measured by tracer gas is not often practicable. Proposes a new method to evaluate this ventilation, based on the normal step-down or decay method. A small control volume of tracer gas is used as opposed to filling the entire space. the local mean age of air is then measured in a study of the transient decay curve of the tracer gas concentration.
This study compares the characteristics of two tracer gases - sulphur hexafluoride (SF 6), and nitrous oxide (N20) – whose densities are different from that of air (i.e. 5.11 and 1.53, respectively). The study is based on exclusively experimental work; and concerns the behaviour of the two gases with regard to their distribution and dispersion in an experimental cell, incorporating into the comparison method an index that is intended to characterise the ventilation of an enclosed space, namely ventilation etfectiveness,
The reintroduction of toxic gases emitted from roof stacks can significantly affect the quality of the air inside a building. The determination of a safe distance between the sources of pollution and the fresh air intakes is based on a complex exercise that must take into account several wind, physical and topographical factors. Estimates of maximum concentrations as a function of downwind distance from a stack can be obtained using empirical models provided by the American Society of Heating, Refrigerating and Air Conditioning Engineers [ASHRAE, 1997](1).
A great deal of the literature on general ventilation expresses the adequacy of the volumetric flow rate of air in terms of the number of room air changes per hour. Although the concept of air change rate has very little relevance to the control of contaminants as it relates to the size of the room and not to the scale of the problem, the overall amount of air entering and leaving a workplace is of fundamental importance in assessing the quality of the working environment.
The present study deals with indoor air quality and is mainly based on an experimental work. The experimental set up is a full scale test cell with a ventilation system which comprises a fixed air supply and a mobile extract. A source of pollutant continuously supplies tracer gas at the centre of the cell. We carried out 12 tests under steady state and with various conditions. The test parameters were the exhaust location, the fresh air now rate and the supply air temperature.