The attribution of pollutant concentrations on buildings from local traffic - Effects on ventilation requirements - A Wind Tunnel Modelling Study

This paper describes an analysis using the BRE Pollution Dispersion Wind Tunnel to estimate pollution concentration patterns on buildings in urban arrays due to local line sources of pollution, typical of vehicular traffic emissions. The experimental procedure involved measurements of both pressure and concentration patterns on building forms in urban arrays, intended to provide information on the ingestion of pollutants into buildings in urban areas. A series of individual contaminant sources was used to represent the line source so that the spatial contribution of each part of the line source to the total exposure could be identified. Two line sources were considered: one of which was directly next to a test building located in the urban array and a second, which was located one street away. It was possible to estimate from the measurements the regions of building faces that would be acceptable or otherwise as locations for air intakes for natural or mechanical ventilation. In the former case, regions of relatively high pressure and low contaminant concentration are required at low levels around the building. The results were used to assist in providing guidance on determining acceptable ventilation air intake placement for both natural and mechanical systems. The placement of air intakes was found to be critical for a line source placed directly adjacent to the test building. For this situation the only suitable location to minimise the ingress of traffic pollutant was at high level. However, for buildings located only one or two streets away, surface concentrations were found to be relatively uniform and hence, with respect to vehicle emissions, the placement of intakes was considered to be less critical.