Describes the API Test Laboratory Accreditation Program (PTLAP), a voluntary accreditation program open to all laboratories doing tests on petroleum products. The PTLAP objective is to verify the quality of test results from petroleum testing. API 1512 sets forth the program requirements for laboratories that wish to be recognized by API as meeting specific industry requirements for testing, measuring, and inspecting petroleum products. Program participants must pass an on-site assessment before accreditation is awarded and must have been an established quality system. API 512 provides criteria for qualification & selection of assessors, conduct of on-site assessments, the evaluation of laboratories leading to accreditation, continuance of accreditation, and the monitoring and surveillance of accredited laboratories.