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.

The possibility of unacceptable internal air pollution levels can cause concern at the design stage given the potential for cross contamination between building exhausts and ventilation intakes is there. The complexity of airflows around buildings, however, makes it extremely difficult to predict the contamination levels at the intake locations. This paper reports a wind tunnel technique using a model of a proposed building to determine the pollutant levels expected at various inlet locations due to the re-ingestion of noxious emissions from its two stacks.

Once the flow-pressurization characteristics of a building are known, the largest uncertainty in predicting air infiltration is the effect of wind shelter from nearby buildings. To study the effects of wind sheltering a large data set of hourly air infiltration and meteorological measurements were made for a row of test houses located on an exposed rural site. This configuration produces strong variations in wind shelter as the wind direction shifts from along the row to perpendicular to it.

Conventionally used thermal anemometers are able to measure velocity, but cannot determine direction. In the present study, a new kind of thermal anemometer is presented which consists of a 38mm-diameter sphere with 12 NTC resistances on its surface. Each of them is a single Constant Temperature Anemometer which takes measurements of the local heat transfer on the surface depending on the position on the ball.

Air infiltration and ventilation has a profound influence on both the internal environment and on the energy needs of buildings. In most electrically heated high-rise residential buildings, in cold climates, during the peak winter conditions (below -18 deg C ambient temperature and above 15 km/hour wind velocity), the air infitration component contributes to heating load by 10 to 28 w/m2 - roughly 25 to 35% of peak heating demand. Any reduction in such uncontrolled air infiltration, without sacrificing indoor air quality, will have potential to reduce the peak heating demand.

Simplified, physical models for calculating infiltration in a single zone, usually calculate the air flows from the natural driving forces separately and then combine them. For most purposes-especially minimum ventilation or energy considerations-the stack effect dominates and total ventilation can be calculated by treating other effects (i.e. wind and small fans) as perturbations, using superposition techniques. The stack effect is caused by differences in density between indoor and outdoor air, normally attributable to the indoor-outdoor temperature difference.

Mechanical devices such as exhaust fans and air handlers interact strongly with natural infiltration. In the past, the effects of mechanical systems have either been treated separately from those of natural infiltration or have been combined using simple models. This paper extends the theory of the interaction of unbalanced mechanical systems with stack-driven infiltration. The effects of leakage distribution and the flow exponent on fan efficiency are discussed. A simple model for combining the two effects is presented and compared with two previously proposed models.

This paper describes the application of numerical models to predict the ventilation rate and internal air movement patterns for a naturally ventilated industrial building and compares the results with measured data. Two modelling techniques have been employed. Firstly, a zonal network model (HTBVent), using leakage area data derived from fan pressurisation measurements, was used to predict the time varying ventilation rate in response to variations in wind velocity and internal-external air temperature difference.

The study recommends adoption of the new higher ventilation rates, but with the use of alternative occupancy densities. To verify compliance with Standard 62-89, the study recommends the method of taking a ratio of temperatures to determine percent outdoor air with a total supply air measurement to determine supplied outside air for each air handler serving the building.