Natural ventilation of inhabited rooms is studied with regard to its dependence on wind velocity and temperature difference between the interior of buildings and outside air. On the basis of simultaneous aerosol and carbon dioxide measurements an attempt has been made to separate the two components of air exchange: ventilation through walls and ventilation through clefts and chinks.
Reports measurements of air change rates made on approximately 250 dwellings, occupied by low income households in 14 cities, in all major climatic zones of the United States. Two types of measurements were used : a tracer-gas decay technique using air sample bags and a fan depressurization test that measures induced air exchange rates. Shows that for this group of dwellings natural air infiltration rates have an approximate lognormal distribution.
Outlines the problem of assessing the rate of heat loss from dwellings due to ventilation. Discusses the mechanisms and pathways of ventilation and ways of controlling air infiltration. Reviews methods of measuring ventilation using tracer gases. Discusses qualities of ideal tracer gas and three automated measuring systems. Reviews some experimental results obtained from the SEGAS test house. Describes house and measurement method. Finds sealing house reduced ventilation rates by between 30 and 45 per cent.
Describes method for measuring the direction and volume of air flows in a building with several rooms. The method uses carbon dioxide as a tracer gas produced from dry ice in each room. Over a period of 2-3 hours the concentration of gas in each room is measured every ten minutes. Gives equations for calculating air flows between rooms and some results of tests made on a flat.
Discusses the use of a tracer to measure the dispersal of air pollutants. Suggest use of Freon-12 or sulphur hexafluoride as tracer. Describes release of tracer, collection of samples in bottles, concentration of sample and analysis in gas chromatograph. Gives results of field trial and concludes that test method is very promising for studying local air movements.
Describes method of estimating ventilation rate using organic vapours as tracer gases and ultra-violet absorption to measure concentration. Gives table of absorption of different vapours. Suggests estimation using a test paper. This method is less precise but requires a minimum of apparatus.
Briefly reviews methods of estimating infiltration rates in dwellings. Describes tracer gas method using methane. Gives results of measurements of air change rate made in houses in Minneapolis, Kansas and Denver. Concludes that technique works well for measuring residential infiltration.
Describes a photo-electric technique for instant determination of contaminant concentration in wind tunnel studies of stack gas dispersion. A roving sensor is used to measure the light scattered by the particles of oily aerosol representing theprototype stack effluent. The minature probe has a noise level of only one hundred thousandth of the full linear range of the output signal for a time constant of 5s. Device is also suitablefor measurement of fluctuating flow properties, such as turbulence, where a high frequency response is required.
Reports investigation of the relative effectiveness of wall gratings and flues as means of naturally ventilating unheated closed rooms. Ventilation rates of several rooms were measured using carbon dioxide as tracer gas and wind speed and direction were recorded. Presents results and finds for the flue, ventilation increased with wind speed irrespective of direction. For grating, ventilation rate increases slowly with size of grating and is dependent on both wind speed and direction. Concludes flue with base opening of 15 sq.ins. is as efficacious as grating having 50 sq.ins.
Describes the basis of operation of electron absorption detector and the nature and causes of the erroneous and anomalous responses it may generate. Suggests pulse sampling technique asan alternative method of analysis. This retains the sensitivity of the simple low potential ion chamber method, but is substantially free of errors and anomolous responses. Describes the basis of this improved method and gives an account of the technique for its use in quantitative and qualitative analysis.
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