Open-path infrared gas sensors have recently become commercially available for offshore applications, but most operators are still unfamiliar with their use. The principle of operation of this type of sensor is reviewed. They have several significant advantages over conventional point-type gas detectors; they are failsafe, immune to poisoning by airborne contaminants, and they are able to give much more effective area coverage than point detectors. Results are presented of experiments to determine their response to realistic gas releases in large enclosures. The results indicate that they have greater sensitivity and faster response than conventional detectors. These advantages are examined, and the practical application of this type of detector to the protection of offshore installations is discussed.