PR1989

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 demand controlled air ductwork should be so dimensioned that the flow controllers have good flow and acoustical operation conditions. From the air flows in a room and its highest permissible sound level, the highest differential pressures allowable to the air flow controllers (duct air flow controllers and terminal devices) are selected.

The paper compares air infiltration rate measurements with air leakage measurements in a modem industrial building. In each case the tests have been performed firstly with the building 'as-built', and then with the major leakage components sealed. The building investigated was of a cladding wall construdion with U-values of 0.6 W.m^-2.K^-1 for both the walls and roof. It had a floor area of 466 m². The volume was 3050 m³. Tracer decay tests and constant concentration methods (both using N20) were performed in the building to establish the air infiitration rates.

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.

France is one of the European countries where ventilation has the most advanced regulation. Vertical ducts have been used for a very long time, making easier the transfer from passive to mechanical ventilation ( which covers now 90 % of the blocs of flats and 70 % of the individual housing) . 1969 regulation has been based on a continuous air exhaust from the service rooms and air replacement through inlets in the habitable rooms. This has never been changed since then and is a part of french regulation's features.

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.

This paper explores the results of air infiltration and ventilation research carried out in Canada over the last decade and specifically examines its application to low-rise residential buildings. With Canada's cold climate, the reduction of space heating costs by dealing with air infiltration and ventilation issues in residential buildings is particularly important and has been the subject of government and industry initiatives. The results over the last decade have been gratifying.

The climatical conditions in Sweden are such that it has almost always been necessary to tighten the houses quite thoroughly in order to avoid cold-draught and to make as good use of the heating as possible. Devices for intentional ventilation, such as ducts for the exhaust of "used" air, have been installed in Swedish houses for centuries. Thus the concept of infiltration and ventilation is not a new one. The more general introduction of central heating in the beginning of this century led to a relatively high degree of dependance on imported fuel.

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.

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.