Spatial variation of CO concentrations within an office building and outdoor influences

This paper presents the results of a monitoring study to assess the spatial variation of CO concentrations within the Westminster City Council building, an office building close to two busy roads in Central London. In general, CO concentrations and correlations with outdoor CO were found to decrease both horizontally and vertically throughout the building away from the busy roads, while the time delay between outdoor and indoor peaks generally increased. This indicates that, within a building, the protection afforded by the building shell to outdoor pollution may be increased away from busy roads. Additionally, the local meteorological conditions were observed to influence significantly the CO concentrations. In particular, south-easterly winds resulted in the highest indoor and outdoor levels, although the highest I/O ratios were for north-westerly winds. (c) 2006 Elsevier Ltd. All rights reserved

High Resolution Modelling of Traffic Emissions Using the Large Eddy Simulation Code Fluidity

The large eddy simulation (LES) code Fluidity was used to simulate the dispersion of NOx traffic emissions along a road in London. The traffic emissions were represented by moving volume sources, one for each vehicle, with time-varying emission rates. Traffic modelling software was used to generate the vehicle movement, while an instantaneous emissions model was used to calculate the NOx emissions at 1 s intervals. The traffic emissions were also modelled as a constant volume source along the length of the road for comparison. A validation of Fluidity against wind tunnel measurements is presented before a qualitative comparison of the LES concentrations with measured roadside concentrations. Fluidity showed an acceptable comparison with the wind tunnel data for velocities and turbulence intensities. The in-canyon tracer concentrations were found to be significantly different between the wind tunnel and Fluidity. This difference was explained by the very high sensitivity of the in-canyon tracer concentrations to the precise release location. Despite this, the comparison showed that Fluidity was able to provide a realistic representation of roadside concentration variations at high temporal resolution, which is not achieved when traffic emissions are modelled as a constant volume source or by Gaussian plume models