This final rule requires that each compressor building in a gas pipeline compressor station have a fixed gas detection and alarm system by September 16, 1996, unless the building has at least 50 percent of its upright side area permanently open, or is in an unattended field compressor station of1,000 horsepower or less. The history of reported incidents at compressor stations shows a potential for leaking gas to accumulate undetected inside compressor buildings. The purpose of the gas detection and alarm systems is to detect mixtures of gas in air and warn persons before a mixture reaches the flammable range.