Area Gas Detection Placement Optimization using Computational Fluid Dynamic Modeling
Daniel Hall; Steven Trammell
(Chemistry & Industrial Hygiene, Inc,, Wheat Ridge, CO (Hall, Strode) / BSI, Austin, TX (Trammell))
Area Gas Detection Placement Optimization using Computational Fluid Dynamic Modeling Daniel Hall, PE CIH Chemistry and Industrial Hygiene, Inc. Cassidy Strode, PSE Chemistry and Industrial Hygiene, Inc. Andrey Korchevskiy, PhD, CIH Chemistry and Industrial Hygiene, Inc. Eric Rasmuson, MS, CIH Chemistry and Industrial Hygiene, Inc. Steven Trammell, PE, CSP, CCPSC, CHMM BSI EHS Services and Solutions Gas detection in semiconductor factories is a critical component of overall risk management for providing personnel protection. Codes and standards, such as the International Fire Code and NFPA 318 provide minimum requirements for gas detection and mandate continuous detection in areas where hazardous gases are used, both within exhausted enclosures and in ambient room areas. Typical strategies are to set detector alarm points at levels that provide early warning of leaks and to allow for rapid response to events, such as shutting off gas sources, with higher set points requiring area or site evacuation. Placement of sensors within exhausted enclosures is relatively straightforward since air flow, and therefore gas from a leak event are designed to travel towards the exhaust port. Within tool enclosures and gas cabinets, even small leaks are reliably detected since the location of the detection point at the exhaust exit is close enough to a leak that significant dilution will not have occurred. Area leak detection is more challenging, since there is much more air volume providing dilution, and air flow dynamics are complex. A major factor impacting air flow is the considerable congestion of piping and equipment located in the subfab space, making placement of detectors in the flow path of a potential leak a difficult task. Computational fluid dynamics (CFD) is a software tool that is unique in its ability to customize a three-dimensional space with as much geometric detail and physics of the environment, as necessary, to appropriately simulate realistic airflow and gas dispersion. In this presentation, we will discuss the use of CFD modeling, to model complex air flow pathways in a typical subfab or chase, which will then allow for more effective placement of gas detectors.