Simulating transient particle deposition/re-suspension in indoor environments

The deposition and resuspension of particles are important factors in the determination of airborne concentrations resulting from accidental and intentional contamination of a building. Most multizone airflow and contaminant transport modeling software treats particulate contaminants as gases, and may not possess the capability to track the cumulative amount of aerosol deposited which is needed for the simulation of transient resuspension processes. A methodology is described for implementing particulate dispersion modeling in a transient, multizone simulation that is consistent with these limitations. The key elements of the method are the calculation of particulate source/sink values in the form required by the simulation software and the use of an iterative procedure to establish the transient surface reservoir concentration. The method is demonstrated and tested using a widely used public domain, multizone modeling program, CONTAM 2.1. It is shown that, although somewhat cumbersome given current capabilities, this method produces reasonable results. Modifications to existing software capabilities required for automated implementation of resuspension are also recommended.