Combustible gas dispersion in residential occupancies and detector location analysis

Recent experiences with combustible gas releases in residential buildings have led to a proposal for NFPA Standards Development for locating combustible gas detectors and consensus on installation location requirements. NFPA has initiated a project on detector location and installation, NFPA 715 “Standard for the Installation of Fuel Gases Detection and Warning Equipment”, similar to the Standard NFPA 720, "Standard for the Installation of Carbon Monoxide (CO) Detection and Warning Equipment." To date, technical analysis for justifying combustible gas detector installation location is lacking to support standards development. This study is proposed to address the residential installation criteria for these devices and systems.

The present study uses computational fluid dynamics (CFD) to quantitatively evaluate gas detector performance as a function of placement in residential occupancies. Natural gas and liquefied petroleum gas releases are simulated in different residential structures and gas concentrations are tracked at numerous potential detector locations within these structures to evaluate which locations are most effective for reliable and early detection. Over 250 CFD simulations were performed with a wide range of plausible leak types and environments to produce robust technical bases upon which gas detector location recommendations can be made. 

A hazard-based approach was applied to compare the performance of gas detector installation locations. More specifically, this study quantified detector location performance based on 1) the ability of a detector location to detect before certain hazardous conditions arise and 2) the ability to provide sufficient response time prior to the hazardous conditions arising.