PR1996

In the urban environment, there is strong evidence that fine particulates associated with vehicular emissions are linked with respiratory problems and an increase in mortality. The population sector most at risk is the elderly who spend much of their time indoors; consequently, the infiltration of these particles and their subsequent behaviour indoors is of primary concern.

Air quality, air flows in buildings, and ventilation are most important topics. Good air quality is however critically dependent also on other things than ventilation, e. g. source strengths, as is well known. The theme of our conference could also lead to the assumption that there is a simple connection between ventilation and air quality. As the public tend to see ventilation systems as responsible for bad air quality, it is important to state that there is no general criterion for good air quality possible to use in practice to control ventilation processes.

Low emitting building materials have contributed to the reduction of indoor air contaminants, and in many countries gas ranges and gas cookers are rarely used. As a result, in buildings located in urban environments, a considerable part of the contaminants in the indoor air may originate from the outdoor air. In urban areas buildings are exposed to high concentrations of a large number of contaminants, especially during traffic peak hours.

A condition often assumed when designing a naturally ventilated building is where air enters at low level and leaves at high level due to the stack effect. It then follows that, at upper levels, the air may be relatively 'stale' since it has previously passed through the lower storeys. An analogous situation may arise when wind is blowing, in which the air entering through the windward face becomes stale as it passes through the building to the downwind sections. It is not well understood how ventilation may, in reality, be affected by this.

The comparison of the performances of ventilation systems must take into account different issues. For indoor air quality, different kinds of pollutant sources have to be defined. To make an evaluation of the results, the best approach is to consider the people exposure. Four generic pollutants are taken into account : rooms components or furniture, human metabolism, cooking activities, passive smoking. As the definition of the unit for each pollutant is free, it is useful for their comparison to press them on a common "normalised" basis.

A naturally ventilated three level office building has been used to study basic stack ventilation configurations and the interaction between ventilation and the subsequent cooling of the building structure in summer. The research was performed in the framework of a European project on passive cooling of buildings and the objective was to validate simple ventilation algorithms and to give an experimental basis to design guidelines for night cooling techniques.

The study concerns the ventilation of a parallelepiped shape room by means of several systems whose supplying and extracting methods differ, so the different thermic conditions applied to limits. To qualify the efficiency of each of these systems in relation with the various current criteria, we carried out measurements by means of a tracer gas, both with a transitory and a permanent flow. At the same time, numerical simulations were carried out by means of a CFD code which solves the equations of the fluids mechanic, material and heat transfers associated with flows.

In response to complaints about poor air quality in bus termini, the Hong Kong Government is considering imposing legislative control over ventilation system design and operation of bus termini in Hong Kong. However, there are, as yet, no relevant air quality criteria and ventilation system design guidelines for Hong Kong. In this paper, measured air quality data for 5 semi-enclosed bus termini are reviewed. This provides a picture of the prevalent air quality in bus termini.

This paper presents the special needs and difficulties concerning cooling and ventilation of the SwissMetro high-speed ground transportation system. SwissMetro is based on four complementary technologies: a complete underground infrastructure, a partly evacuated tunnel system to reduce the aerodynamic drag of the vehicle with a maximum speed between 400 and 500 km/h, linear electric motors and a magnetic levitation and guiding system. Due to high internal and external heat loads permanent cooling and air-conditioning of the vehicle is required.

Adequate ventilation with the "right amount of air, to the right place and at the right time" are important factors for achieving a good indoor climate. Thus it is of prime importance that the ventilation system is working properly. Using traditional methods, it is a very time consuming, and some times even impossible, task to balance ventilation systems to achieve correct air distribution. In most countries the growing concern about Indoor Air Quality has resulted in Building Codes demanding increased ventilation rates.