Atmospheric tracer release techniques have been used to quantify low-level fugitive methane emissions from components and facilities in all sectors of the natural gas system in the United States. The emission data are collected as part of a program to extrapolate the emissions from the entire U.S. natural gas industry and thus reduce uncertainties in the environmental impact of increased natural gas use. In these experiments, the total methane emission from a site is measured by releasing a tracer gas (SF6) at the natural gas facility to simulate the source. Both methane and tracer levels are measured with real-time instruments deployed in a mobile laboratory downwind of the site. A large range of emission levels for the different sectors of the entire system was determined. Within any one group of a particular facility type there is also much variability in the emission rates. The exact nature and number of gas system components in a facility are important factors in determining its emission level.