Simulation and analysis of airborne cross-contamination routes due to the operation of building drainage and vent systems

Recent concerns about the role of the drainage and vent systems installed in high-rise and other buildings in the possible spread of airborne contamination have highlighted the need for simulations capable of predicting system response when subject to multiple and random events. Such simulations would allow designers to predict the possible contamination routes established as a result of failures of the system, e.g. trap seal loss and/or the influence of dried-out traps. In addition, the simulations proposed would provide diagnostic tools in the event of cross-contamination. Mathematical solutions are used to simulate the system unsteady water and entrained airflows, and the application of these simulations to predict likely contamination routes. The AIRNET simulation is employed to represent the unsteady air and water down-flow conditions in the network, the associated propagation of air pressure transients and trap response. The simulation can provide a design and standards development tool as well as a forensic and diagnostic tool for the investigation of suspected cross-contamination. The simulations confirm that cross-contamination routes result from normal operation and random failure conditions, including system surcharge and trap depletion due to, for example, poor maintenance. It suggests that simulation predictions have an important role in ascertaining potential hazards, as well as a forensic role.