Case Study of Dense Hazardous Gas Dispersion in Large Indoor Spaces: Ventilation Layout Analysis with Modeling

The safety of large indoor workspaces hinges on ventilation layout and airflow organization, particularly for dense contaminants that pool near the floor. This qualitative, full-scale case study evaluates chlorine (Cl2) capture using supporting CFD and visualization experiments in a 20 × 13 × 9 m hall. Four exhaust arrangements—low, mid, high, and all levels combined—were tested under two modes: a single grille at 12,000 m3/h and three co-located grilles at 4000 m3/h each (total 12,000 m3/h), with and without an auxiliary supply (2000 m3/h). Removal performance was sensitive to exhaust elevation: low-level extraction consistently confined the plume near the floor, while distributing the same total flow across three levels achieved comparable or improved capture; mid/high extraction was less effective. A practical extraction radius of ≈5 m was identified, and the auxiliary supply improved outcomes only when steering the plume toward the low grille. CFD results showed that, regardless of the lower grille’s duty, the inlet concentration at the low grille was about twice that at the middle grille and more than four times that at the upper grille; in the three-grille configuration, the upper grille received negligible contaminant. These full-scale findings provide geometry-first guidance for dense-gas control in high-ceiling, large-volume spaces.