This paper presents a new technique for supply of outdoor air directly through external walls into a dwelling room without any draught problems. A new type of air inlet unit has been developed based on the experience from the study of indoor climate in the " Stockholm Project" . This Swedish experiment including six new residential buildings, where the indoor climate together with different solutions for ventilation is evaluated, shows that draught from air inlets is one of the greatest problems with bad indoor climate.

The air change rate in existing, older blocks of flats having natural ventilation has been measured by the tracer gas method. Measurements were made in the buildings in as-found condition. The average air infiltration rate was 0.26 air changes/h (with the ventilation ducs closed), with an overall ventilation rate of 0.47 air changes/h. The average overall ventilation rate is very close to that recommended on the basis of health requirements, although values both above and below this are encountered in many flats.

An up-to-date design concept for office buildings results in a very low energy consumption and provides a better indoor climate at the same time. This new concept is based mainly on two design features: An extremely well insulated building envelope decouples the indoor climate from the outside climate to a high degree during all seasons and weather conditions. The second element of this new design concept is the HVAC-system: The source-dominated displacement ventilation provides a better comfort and, as a cosequence of its high effectiveness, is very economical.

Measurement methods based upon multiple tracer gas techniques have become an established branch of the study of air infiltration and interzonal air movements. Three general groups of techniques have emerged, namely constant concentration, constant emission, and decay. Of the decay type group of techniques, several methods of deriving airflows from measured concentration/time curves have been suggested.

Ventilation in a building enables to renew the air it contains by means of a natural exchange of air (depending on weather conditions and climate) or a forced exchange using mechanical appliances. This exchange of air must range between minimum air purity and maximum economical limit of dispersion (ventilating means cooling) without causing currents of air, unbearable for the people in the room, which would worsen thermal comfort.

This paper describes the development of a microprocessor-controlled tracer gas system which is capable of collecting a large number of tracer gas samples at short or long intervals. The system can be used for accurate measurement of air flow through openings, e.g. cracks, windows and doorways.

A comparison of three injection manners, step-up, step-down and pulse, for determination of the mean age of air was made by using nitrous oxide and sulphur hexafluoride as tracer gases. The concentrations of nitrous oxide and sulfur hexafluoride were simultaneously measured with a dual-channel IR-analyzer. Tests were carried out in a test chamber with air change rates of 3 h-1 and 5 h-1. The tracer gases were injected under three conditions: into the inlet air and directly into the room with and without extra mixing fans.

1979 a project was launched at Technological Institute, Copenhagen with the purpose of developing a method for continuous measurement of air change rates in occupied dwellings. Today - 10 years later - we can introduce the first generation of mass-produced measuring equipment performing measurements of air change rates employing the method of constant concentration of tracer gas. The principles used in the first model, which was introduced 1981, are largely identical to those used in the latest model.

The AIVC nowadays is an established Centre on infiltration and ventilation research. It is well known throughout the world. This position has not been reached easily. But years of hard working and critical managing of the Centre were a necessity. Goes on to discuss the future development of the Centre.

This paper examines some designs which lead to indoor air pollution and exhorts mandatory maintenance of all building services which determine the health and safety of the building occupants as anintegral part of our city bylaws. Effect of poor maintenance of some of these systems on the indoor air quality is examined together with the effect of the interruption of the ventilation fans for energy conservation pwrposes, not always done legally.