The first part of the paper will show some aspects of experimental research on air distribution in ventilated rooms. The study has been carried out to get an understanding of the air movement and the ventilation effectiveness by means of tracer gas measurements. It has been investigated the velocity and the distribution of the concentration in a two-dimensional isothermal flow issue of a linear supply opening. The second part of the paper will describe a proposed zonal model in 9 zones.

The work presented in this paper is aimed at the definition of tracer gas experimental procedures for measuring the air change rate, the age of air and the air change efficiency in real buildings under mechanical ventilation conditions. The measurement procedures, based on the decay method, were validated in a special experimental chamber and implemented in two rooms of a building under real operating conditions. Measurements of volumetric flow rate through the air ducts of two buildings, performed by means of the constant emission rate method, will be shown and commented.

The use of local exhaust is considered to be the most effective way to control pollutant dispersion from intense sources, such as in kitchens, in toilets, as well as in copy machine rooms. The optimum air exhaust rate required to prevent pollutants from escaping into the major occupant areas very much depends on the natural air exchange rate(AER) between the hooded room and the major room space. This paper presents a mathematical model and a test procedure of using tracer gas technique to quantify the AER.

The homogeneous emission passive tracer gas technique is described. This technique relies on an even distribution of constant tracer gas emission rate within the object to be measured, so that the emission rate per volume unit is constant. The local steady state concentration of the tracer gas is directly proportional to the local mean age of air and the emission rate per volume unit.

Full scale measurements of air flow velocities, temperature, intensity of turbulence and air exchange rate are carried out on two rooms with different types of ventilation located in the department of architecture at Chalmers University of Technology. The measurements have shown that mixed ventilation gives variable mean flow velocities with a high risk of draught as compared to the room provided with displacement ventilation. Air exchange rate for the room with displacement ventilation is obtained from tracer gas monitor by employing decay and constant emission methods.

The problem of sensation of draught in ventilated spaces is connected to inappropriate velocities in the occupied zone. In Scandinavia, velocities higher than 0.15 m/s are said to be an indicator of that occupants are likely to feel discomfort. Therefore knowledge of the flow field (both mean velocities and fluctuations) is necessary. Both experimental and numerical analysis of the flow field in a full scale room ventilated by a slot inlet, with two inlet Reynolds numbers 2440 and 7110, have been carried out .

Many modern buildings in the Nordic countries have mechanical ventilation. Passive stack ventilation is, however, an accepted ventilation system in the Nordic countries according to the current building codes. The building authorities need to be able to supply guidelines on natural ventilation systems in modern buildings, in order to fullfill the requirements on a healthy indoor climate at a reasonable energy cost. Therefore a project was initiated by the Nordic committee on building regulations.

Ventilation is necessary to provide a good indoor air quality to occupants in office buildings but is however a major energy consumer. In that manner, ventilation in itself can contribute to much more than 50% of the energy consumption for heating in well insulated office buildings. Likewise, the general trend in standards to augment ventilation requirements would still increase its energy costs. Thus, it seems obvious that an intelligent control of ventilation in office building allows to obtain substantial reductions of energy consumption.

To ensure indoor air quality an efficient ventilation system should provide fresh air in those parts of a room where it is required. To assess whether the ventilation system fblfils the main objective, different definitions of local ventilation efficiency (the local mean age of air, the local ventilation rate, the local purging flow rate and the local air exchange rate) are reported in literature.

The acceptance and appreciation of ventilation systems is mainly determined by the perceived indoor air quality, thermal comfort and noise. Noise in relation to ventilation systems can be divided into three categories: outdoor noise (entering the dwelling through ventilation openings, cracks, mechanical supply and exhaust openings etc.); noise generated by components of the ventilation system; the impact of ventilation systems on sound reduction of partitions (between dwellings, rooms etc.). Depending on the type of ventilation system, one or more of these aspects are of concern.