CFD Analysis of VX Gas Dispersion in an Indoor Environment

VX, a highly persistent and lethal nerve agent, presents a severe threat in enclosed spaces during chemical attacks or accidental releases. However, its dispersion behavior within indoor environments remains poorly understood, limiting the effectiveness of mitigation and response strategies. This study introduces the first transient three-dimensional computational fluid dynamics (CFD) analysis of VX gas dispersion and removal in a confined space, defining novel safety metrics: danger time (time to reach a toxic 10 mg/m³) and safe time (time to decline below a safe 0.1 mg/m³). Employing the k-epsilon turbulence model in COMSOL Multiphysics, we investigated the effects of air inlet velocity (0.5–1.5 m/s), inflow VX concentration (100–300 mg/m³), and initial VX concentration (500–1000 mg/m³) in a validated room-scale model. Results reveal that elevating inlet velocity from 0.5 to 1.5 m/s reduces safe time by 67.1% (40.8 to 13.4 min), enhancing decontamination, while increasing inflow concentration from 100 to 300 mg/m³ accelerates danger time by 70% (0.2 to 0.06 min), amplifying risk onset. Higher initial concentrations extend safe time by 9.3%, reflecting slower dilution. VX accumulates near walls, driven by mixing effects, identifying critical hazard zones. Moreover, the results show that incorporating obstacles into the indoor environment increases both the danger and the required safety times.