English

Introductory talk on the indoor air quality problem. Compares risk of radon pollution in houses to the risks of smoking tobacco, and gives a definition of levels of concern. Mentions filtering of indoor air by means of an air-to-air heat exchanger, the interaction between ventilation and sources, e.g. unvented combustion heaters and carbon dioxide emissions; measurements of nitrogen dioxide are compared, and formaldehyde concentrations in 28 different commercial buildings.

Describes factors to be taken into account for air conditioning and heating in a theatre. Nature and purpose of the building call for an adequate supply of conditioned outdoor air, with a total supply air rate up to 69,000 m3/h. Economical use of energy was stressed. Detailed description of the problems involved with the auditorium and stage shaft are given.

Evacuation of people from their homes and workplaces is a standard response to the hazards created by the release of toxic gas. However, by staying indoors a person can take advantage of the clean air stored within the house volume, as well as the damping the house provides for sudden changes in outdoor toxic gas concentration. The relation between indoor and outdoor concentration is explored in this study, where it is shown that in most cases the risk of exposure to high concentration levels is substantially reduced by remaining indoors during the entire period of toxic gas release.

Notes field evidence of increased condensation in houses with reduced ventilation and increased thermal insulation installed to conserve energy. Treats the possible long term effects. Gives advice on taking into account the whole package of heating and ventilation of the property when energy conservation measures are being contemplated.

Uses a model to estimate the incremental risk of lung cancer associated with increased radon concentrations in indoor air resulting from decreased air infiltration caused by increased air tightness of dwellings. Gives results for selected changes in the air exchange rate. Discusses findings.

Summary of an APCA International Speciality Conference. Contains information on some relatively unfamiliar trace gases and fungi, as well as on the better known indoor air pollutants. Studies range from those on human health tothose concentrating on pollutant emissions to those addressing building ventilation. Papers also cover sick building syndrome and pollutant and ventilation surveys.

The design of a low cost ventilation air heat exchanger which utilizes plastic sheets as the heat transfer surface is presented. Laboratory tests on such acounter flow heat exchanger have demonstrated very high values of overall heat transfer coefficients, heat exchanger effectiveness, and temperature recovery when the flow is laminar and buoyancy effects assist the heat transfer. The costs of such heat exchangers would make them attractive for many building applications.

A study was made of one hundred subjects who were exposed to air flow with a turbulence as occuring in typically ventilated spaces. Turbulent air flow is seen as more uncomfortable than laminar flow. Each subject participated in three experiments at air temperatures of 20, 23, and 26 degrees C, withvarying air velocity and turbulence intensity. Recommends a reduction of velocity limits specified in existing standards.

Recent work by the National Radiological Protection Board indicates that higher than average levels of exposure due to radon occur in the South West. West Devon District Council has undertaken its own survey on radon concentrations to see whether these can be associated with lung cancer incidence. The control of radon gas is likely to have implications for building structure and ventilation. There is a potential conflict between the desirability of increasing ventilation to cut radon levels on the one hand and reducing air infiltration to save energy on the other.

Starting from the premise that condensation in the building envelope is a prime cause of its deterioration, the mechanisms that cause condensation are discussed and control measures explained. The conflicts that arise between some of these measures, the probability of achieving them under realistic construction conditions, and the possible need for fail-safe provisions should complete success not be achieved, are described.