Investigation of the Reduction Time of Sarin Gas Concentration in an Indoor Environment Using Computational Fluid Dynamics

The investigation of sarin gas distribution and the safe time (defined as the time when the sarin gas concentration is less than 1 mg/m³) is critically important for safety and defense purposes. Therefore, in this study, the safe time and sarin gas distribution in an indoor environment were analyzed using unsteady three-dimensional computational fluid dynamics (CFD). Firstly, mesh independence and model validation were conducted, followed by the analysis of gas distribution and concentration in the indoor environment. The results showed that the initial sarin gas concentration and the air inlet velocity have a significant effect on the safe time. By increasing the air inlet velocity from 1 m/s to 2 m/s, the safe time was reduced by approximately 50%, which is attributed to the increased mass transfer and air flow rate in the indoor environment. The safe time was 4.65 minutes at an inlet velocity of 1 m/s, 3.55 minutes at 1.5 m/s, and 2.3 minutes at 2 m/s. Moreover, the initial concentration significantly influenced the safe time, where the safe time for an initial concentration of 10 mg/m³ was 2.3 minutes, increasing to 3.05 minutes for 20 mg/m³ and 3.55 minutes for 30 mg/m³. Therefore, increasing the initial sarin gas concentration from 10 mg/m³ to 30 mg/m³ resulted in a 54% increase in the safe time.