tracer gas

This paper extends the integral mass balance approach to the remaining constant concentration technique. An integral formulation of the constant concentration problem is presented that accounts for the possibility of variation of tracer concentration. This approach leads, in principle, to data reduction strategies that may be expected to improve the accuracy of the constant concentration technique and that may be used to isolate those portions of a given constant concentration data set that are likely to be most reliable.

This paper presents a new approach to determine the interzonal airflows of a multizone system using tracer gas measurements. In contrast to methods proposed earlier, the presented method does not use the mass balance as basis for the least squares problem but identifies the interzonal airflows as coefficients of the evolution equations for the concentrations. Therefore estimating the derivatives with respect to the time from measured data is avoided. Furthermore the concentration can be calculated at arbitrary points in time.

A new passive tracer gas method for ventilation measurements is described. The method utilizes passive tracer gas release from aliquid perfluorocarbon compound contained in a glass vial, equipped with a teflon membrane. Air sampling is also done passively by diffusion through a glass tube containing activated carbon. Quantitative analysis of trapped tracer compound is performed by solvent extraction and gas chromatographic separation using a liquid injection technique. Separation is done with a two-column system and quantitative analysis with an electron capture detector.

Tracergases provide a way to determine airflows in different situations. In some cases it is the only way to get quantitative information. This paper presents two cases in which tracergases are used for measuring the internal leakage in heat recovery units. Internal leakage in heat recovery ventilators (HRV's) for domestic use may cause some problems: - the real quantity of fresh air entering the building is unknown - electrical power for the fans is used inefficiently - smelling air a.g.

We describe the use of constant injection and pulse injection techniques for measurement of airflow in a duct. Tracer-gas measurements were compared with measurements made using a pitot tube and a hot-wire anemometer. Tracer-gas concentration, air velocity and pressure distribution were measured at various distances from the duct wall and inlet. An empirical equation was obtained for the entrance length required to achieve fully-developed turbulent flow and this was compared with measurements made using a pitot tube and hot-wire anemometer.

This article discusses the application of tracer gas methods to industrial hygiene investigations. It introduces the basic concepts necessary to understand the application of tracer gas methods to particular airflow and contaminant movement measurements. It provides an overview of existing methods which can be used to obtain quantitative data on a variety of airflow and contaminant movement related questions which often are of interest to the industrial hygienist.

A new algorithm for the continuous measurement of variable air change rates with tracer gases will be presented. It differs from the constant concentration method by allowing the concentration level to vary according to the air change rate. Also the mixing process of tracer gas within the room under investigation is considered and limited measurement ranges and injection rates of the tracer gas equipment can be accounted for. The new algorithm has a number of advantages, such as quick response to variations in the air change rate and reduced tracer gas consumption.