The effect of external pollution levels on indoor air quality is a subject of growing interest, especially with the increasing application of natural ventilation in urban areas. The analysis described in this paper allows the effects of varying external pollution levels to be estimated for any configuration of ventilation system, natural or mechanical. The analysis takes into account filter efficiency and position, internal pollutant sources, degree of re-circulation and varying fresh air rates.
Gravimetric determination and continuous monitoring of respirable dust in air has revealed that there are high levels of dust at some roadside and indoor locations in urban areas. Furthermore, where high dust levels are measured in roadside samples, high concentrations are also measured in adjacent buildings. The dust levels measured inside a building have been shown to be very closely correlated to ambient levels, and traffic emissions, particularly from diesel vehicles, are the principal source of respirable particulates.
Indoor and outdoor concentrations of respirable particulates and sulfates have been measured in 68 homes in six cities for at least 1 yr. A conservation of mass model was derived describing indoor concentrations in terms of outdoor concentrations, infiltration and indoor sources. The measured data were analysed to identify important building characteristics and to quantify their effect. The mean infiltration rate of outdoor fine particulates was found to be approximately 70 %- Cigarette smqking was found to be the dominant indoor source of respirable particulates.
This review examines the available information relating to the ingress of external pollutants into naturally ventilated buildings. It is part of a project whose longer term aim is to provide guidance on ventilation strategies for naturally ventilated buildings in polluted urban areas. The purpose of the review is to guide this project.
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