Air change rates are measured by an IR-gas-analyser coupled with a microcomputer which is programmed to control measurements as well as data acquisition and evaluation. The implemented programs provide an instant access to results. The experimental equipment is installed in compact form on mobile units. Measurements have been taken in a university laboratory by using the decay- and constant-emission-method to examine air change rates under various conditions. Typical results are presented and show where each of the two methods is more appropriate.
The total air infiltration rates can be determined by the tracer gas decay method, but to measure the influence of inhabitants or convective exchanges between rooms, the constant concentration method is more suitable. In order tomeasure these effects, the Compact Equipment for Survey of Air Renewal (CESAR), developed at the LESO, was used to perform an air exchange analysis on data recorded at regular intervals in up to 10 locations simultaneously. Three tracer gas methods were implemented: decay, constant concentration and continuous flow.
Results from a two-box model for calculation of tracer gas concentrations in rooms are given and consequences of different definitions of ventilation efficiency are discussed. Results from three different series of experiments are presented.
As part of a programme to develop measurement methods for determining the ventilation rates of large buildings, we performed two series of tests in a single-celled laboratory with a volume of 600m3. The first series utilised constant concentration, constant emission and rate of decay tracer gas techniques to determine the characteristics of the infiltration pattern in varying winds and external temperatures. We used both discrete and continuous injection and sampling methods.
A Compact Equipment for Survey of Air Renewal (CESAR) was developed at the Ecole Polytechnique Federale de Lausanne in Switzerland. Controlled by a microcomputer, this apparatus uses tracer gas methods ( decay, continuous flow or constant concentration). Up to ten different locations in inhabited rooms can be monitored simultaneously over extended periods of time, using mainly the "constant concentration" technique. Several air renewal surveys were carried out on different inhabited buildings.
A tracer gas technique has been used for evaluation and characterization of air flow pattern of contaminants penetrating into buildings. As a tracer, sulfur hexafluoride (SF6) was used and detected by a gas chromatograph equipped with an electron capture detector. SF6 was released at suspected points of contaminants origin at a constant flow rate and was detected quantitatively in the room or laboratory of concern.
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