Air pollution levels inside buildings in urban areas: a pilot study

This paper reports the findings of a pilot field study carried out to investigate the internal and external pollution levels in two buildings, one naturally-ventilated and the other air-conditioned and to investigate their relative attenuation of external pollution levels. The study is a precursor to more extensive studies aimed at providing guidelines for the design of energy-efficient buildings with a good indoor environment in urban areas. Concerns about energy usage and C02 emissions from buildings require that adequate indoor air quality is obtained in an optimal manner within low-energy design criteria. There is thus an increasing number of buildings employing natural ventilation strategies. At present, however, little is known about the interaction between indoor air quality and external air pollution. Therefore, no formal guidelines exist on designing for natural ventilation in nondomestic buildings in urban areas with respect to external air and noise pollution. The buildings investigated were adjacent to one another and located near a major road in a city centre where the local air pollution levels were known to be relatively high. During the study, concentration levels of typical urban pollutants, such as sulphur dioxide, nitrogen oxides and carbon monoxide were monitored. Concurrently, measurements of carbon dioxide, ventilation rates, humidity and temperature within the buildings including some measurements of noise and particles were also carried out. Analysis of the data reveals a number of interesting points. The concentrations of external pollutants in the buildings follow the daily external variation, but at reduced levels. Generally, pollutant levels were higher in the naturally ventilated building than in the mechanically ventilated building. However, on a number of occasions, combustion products from heating boilers were entrained into the air-conditioned building via the high level air intake of the ventilation system. This raised the levels of nitrogen oxides and carbon dioxide inside the building to higher than those found externally.