English

Discusses ways of modifying distribution of stack effect through building by design and construction. Suggests many of the problems caused by stack effect could be alleviated byincreasing air tightness of building enclosure and interior separations. Discusses influence of mechanical ventilation systems on stack effect. Shows that pressurization does not eliminate stack effect but alters distribution of pressure differences.

Briefly reviews ways of ventilating buildings. Discusses control of oxygen and carbon dioxide levels and control of odours and airborne particles. Concludes ventilation is an essential element in the design of a building and its services.

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.

Outlines projects at the Division of Building Research to carry out extensive field observations and studies of loads particularly snow loads on roofs and wind pressures and suctions on walls of high-rise buildings. Describes major features of this work including observation methods and some of the results.

Reports an indoor/outdoor sampling program for NO, NO2 and CO in four private houses which had gas stoves. Pollutant gases were measured essentially simultaneously at three indoor locations and one outdoor location. Shows that indoor levels of NO and NO2are directly related to stove use. In some instances levels of NO2 and CO in the kitchen exceeded the air quality standards for these pollutants if data for the sampling periods were typicalof an entire year.

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.

Reports some results of field measurements of radon levels in apartments and houses and shows that summer measurements with high natural ventilation rates are generally lower than winter measurements. Suggests exhalation of radon from building materials can be studied by placing samples of material in closed vessels and following the growth of activity in the vessels. Shows that a ventilation rate of one air change per hour will lower the theoretical maximum level to 0.008 of the unventilated maximum value.

Radon is a radioactive gas which diffuses naturally from all mineral based building materials. States for most homes, concentration of radon is approximately inversely proportional to the ventilation, although this is not valid for very low or very high air change rates. Gives brief results of measurements of concentration of radon in dwellings. Outlines health risks from radon and daughters. Reviews norms laid down in some countries for specific situations. Discusses ways of reducing radon concentrations.

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.