A branched connection is a single air flow passage connecting more than two zones. Its existence in a building has not been a critical issue for the measurement of air flows of single zones, as far as the validity or accuracy of the measurement techniques is concerned. However, with the ever increasing sophistication of building air flow measurement techniques --- which include tracer gas and multifan pressurisation techniques --- and the ever increasing use of them in multizones, it becomes increasingly desirable to examine the effect of branched connections.

Building air flow is directly related to the building energy consumption and indoor air quality. As buildings become increasingly air tight, air flow through building background cracks becomes more important, and can account for up to half of the total building air infiltration. However, background leakage is not well understood, due to the lack of appropriate measurement methods. The multi-fan guarding zone or deduction technique provides a means for testing background leakage distributions, an important parameter for characterising the background leakage.

One of the main problems about air flows pattern studies remains the experimental validation of numerical codes developped for interzone air flow and polluant diffusion prediction. A few years ago, CETHIL developped a real scale experiment made of a 88m² dwelling built in our laboratory hall in a controlled climatic environment.

Spillage of combust ion products from open f lued combust ion appliances represents a source of indoor air pollutants which can cause danger to health. Air extract fans are installed in kitchens in order to remove moisture and cooking smells, but the room depressurisation which they create is a potential cause of spillage. A series of experiments was therefore set up to determine the fan flow rate and internal/external pressure difference at which spillage first occurred in different open flued gas and oil boilers.

The greenhouse effect is one of those topics in environmental politics which are currently worldwide at stake. There are several national concepts aiming at the diminution of CO2-emission in order to lessen the greenhouse effect. One of these concepts is the CO2-reduction programme of the Federal Republic of Germany. With this resolution, passed on November 7th, 1990, Germany's Federal Government aims high: national carbondioxide emission is to be cut back by 25 per cent by the year 2005.

The house dust mite inhabits bedding and soft furnishings in homes. It is implicated as a major cause of allergic asthma. Maintenance of indoor humidity below a level of 7 g/kg inhibits the growth of the mite population. A pilot survey was carried out by EA Technology in cooperation with the Building Research Establishment to investigate the effect of mechanical ventilation with heat recovery (MVHR) both on indoor humidity and mite abundances.

A sudden contamination of the outdoor air by some toxic gas can have several causes. The primary goal of the investigation was to determine the protection afforded by sheltering indoors. The object of a computational approach was a single family house with two floors. Three different models were utilized as computing tools: MOVECOMP to calculate the infiltration air flows, MULTIC to calculate the contaminant transport inside the building and TDYN to calculate the temperature decay of the building.

The amounts, quality and factors affecting of dust accumulation in supply air ducts of eight nonindustrial buildings were studied. The average of surface density of dust settled in supply air ducts was 10.6 g/m² and the average of yearly accumulation rate was 3.5 g/m²*year. The dust contained 82% of inorganic material, which agrees well with the composition of outdoor air dust in down town areas. In straight air duct the surface density of settled dust decreased as a function of distance from the air handling unit (AHU).

The dour threshold value of kitchen exhaust air was experimentally determined during typical cooking situations and tobacco smoking in a dwelling. During cooking, air from the exhaust duct was taken into a sample bag. The dour threshold concentrations of the samples were determined by sensory evaluation using olfactometer and untrained dour panel. Experiments were made both in laboratory and field settings. The largest dour threshold concentration of 168 o.u./m³ was determined during the frying of herring.

A humidity controlled exhaust fan have been tested during the winter season 1991/2. The test have been carried out in a detached one storey house with a flat roof. The relative humidity (RH) have been measured in the following modes: * natural ventilation only* wall mounted fan, setpoint 70% RH, and natural ventilation * fan in the exhaust duct, setpoint 70% RH.The relative humidity levels have been monitored in the shower room and in the other part of the dwelling. The temperatures have been measured in the exhaust duct and in four places in the dwelling.