This action promulgates national emission standards for hazardous air pollutants to regulate hazardous air pollutant emissions from oil and natural gas production facilities that are area sources. The final national emission standards for hazardous air pollutants for major sources was promulgated on June 17, 1999, but final action with respect to area sources was deferred. Oil and natural gas production is identified in the Urban Air Toxics Strategy as an area source category for regulation under section 112(c)(3) of the Clean Air Act because of benzene emissions from triethylene glycol dehydration units located at such facilities. This final rule also amends a general provision in the regulation to allow the use of an ASTM standard as an alternative test method to EPA Method 18 in the National Emission Standards for Hazardous Air Pollutants From Oil and Natural Gas Production Facilities.