A gas sensor network system provides near real-time monitoring of fugitive emissions of VOC compounds in chemical plants and facilities. The present disclosure provides a sensor placement method which determines where to place sensors within a facility. The sensor placement method includes obtaining plant layout, gas composition, meteorological conditions and/or other types of information regarding a facility, determining the types of gas and ancillary sensors needed, and generating the minimum detection distances required based on the sensitivities of the sensors to the gas compounds involved. And, then calculating the minimal number of sensors required for each sensor type with optimized sensor locations to ensure best coverage of potentially leaking components within the facility.