This report provides the results of a two-phased study conducted for the Canada Mortgage and Housing Corporation (CMHC) to examine the practices and variability amongst practitioners of contaminated sites risk assessment in Canada. Phase I consisted of a survey of practitioners in the private and regulatory sectors. The intent of the private sector survey was to characterize the capabilities and experience of private firms engaged in human health risk assessment across Canada.
There are two main soil gases of current concern to human health. These are radon, which is a carcinogen, and landfill gas, which is explosive and toxic. Both can be found at significant levels in the soil below buildings in certain locations in the country. It is a responsibility of the Building Research Establishment to find cost effective ways to protect new and existing buildings from the entry of these gases into buildings.
A three-dimensional drift-flux model for particle movements in turbulent airflows in buildings is presented. The interaction between the carrier air and the particles has been treated as a one-way coupling, assuming the effect of particles on air turbulence is negligible due to low solid loadings and comparatively small particle settling velocities. Turbulence effects are modelled with a standard K-E model. Wall functions are applied at near-wall grid points. Aerosol measurements carried out under turbulent room flow conditions are used to validate the numerical calculations.
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