The GDS 305 system is designed to monitor gas levels from a number of sample-points, targeted at situations where the positioning of conventional gas sensors may not be practical. This may be due to equipment security, cable routing, access for detector head installation/maintenance, harsh environment or a cost effective means of monitoring designated hazardous areas, typically-tunnels, marine applications, underground/high level voids, process control, landfill, multi storey car parks, brewing, horticulture, superstore multi refridgeration units, Bio-fuel storage compounds.