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.
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.
Air is the main transport medium for contaminants in buildings. Minimizing source strengths has first priority, second is to control air flow rates, supply and exhaust, and directions between zones in buildings. Computer simulation models forventilation and pollutant spread in buildings have been proven to give useful predictions. Large measurement campaigns for optimizing ventilation and pollutant problems are complex and expensive. They are often jammed by too many vague parameters influencing the result. The computer models are an alternative and form a supplement to measurements.
Mechanical equipment may influence the airflow between rooms in a number of ways: 1) There is the direct airflow through ducts using supplies and returns. This approach may be just a single pass system where supply air enters and exhaust leave
The COSHH Regulations are concerned with the health of employees in relation to their exposure to harmful substances, particularly airborne contaminants. COSHH places a great deal of emphasis on the control of substances to reduce exposure. Featuring prominently under control is ventilation, whether it be dilution ventilation or localised extract. The Building Services Engineer has and important and prominent role to playunder COSHH in relation to ventilation and control measures, in particular in defining performance criteria and establishing examination and testing procedures.
The main air and contaminant flow paths or the spatial distribution of the age of air (or contaminant) in a room are of great interest to estimate the ventilation efficiency performance. A simple measurement method is presented, which consists to inject or more tracer gases at locations of interest and to analyze the concentration at several other locations, carefully chosen for best accuracy. Response functions can be fitted on these measurements, which are the age of the tracers or of the air or the concentration of the tracers in function of the location.
This paper treats the structure of models for predicting interzonal airflow and contaminant dispersal in buildings. It will discuss the mathematical structure of such models, the use of modem data structures, the application of structured program techniques and the use of object-oriented structures for the development of users interfaces and building description processes.