The work described here concerns the development of fiber sensors and networks for monitoring trace gases such as methane, acetylene, carbon dioxide, carbon monoxide and hydrogen sulphide, all of which are important in environmental or safety monitoring. A 45-point fiber sensor network using a single DFB laser source has been installed on a landfill site to assess the distribution of methane generation across the site, with detection levels from < 100 ppm to 100% methane. The system is currently being extended for carbon dioxide and hydrogen sulphide monitoring. Concurrently, fiber lasers sources are under investigation to provide a single source for several gases using techniques such as mode-locked operation for interrogation of multi-point systems and ring-down spectroscopy for high sensitivity measurements.