A Fire & Gas System (FGS) philosophy provides a solid foundation for the design of an effective gas detection system, which in turn helps protect plant and personnel from gas releases and resulting flammable and/or toxic effects. An FGS philosophy for a process facility that is not fit for purpose or does not have a firm auditable basis can increase the likelihood of undetected leaks incurring risk to personnel or unnecessary expenses for the company. Under-engineering a gas detection system has safety implications, while over-engineering has commercial implications such as increasing capital and maintenance costs without significantly reducing risk.