On the dispersion of a light chemical agent in a semi-closed environment. A theoretical study

Chemical events have significant public health and emergency preparedness consequences; therefore, crisis response planning is of outmost importance. The dispersion of a chemical agent in an indoor environment, near the so-called “human breathing zone” can cause harmful effects to its occupants. The present study examines the dispersion of ammonia (NH3), i.e., a lighter than air, colorless, highly irritating gas with a suffocating odor, in an office. For that, the turbulent flow of NH3 under the influence of the indoor air's circulation has been simulated, using a Computational Fluid Dynamics model, i.e., the Realizable k-e model. On the whole, the study provides estimation and of the NH3 levels in the office, mainly up to the human breathing zone, as well as evaluation of the natural ventilation's contribution in the decongestion and decontamination of indoor air. • The 3D geometric model of the office was created, taking under consideration the office's structure, the equipment's layout, the openings’ positions as well as any other object that could act as an obstacle to the agent's flow. • The domain's 3D Computational Mesh was created and grid independence tests were performed, in order to secure the solution's independence from the grid. • The chemical agent's flow was simulated and the results were compared to the IDLH index and the AEGLs set for ammonia.