The American Petroleum Institute (API) Manual of Petroleum Measurement Standards (MPMS) Chapter 14.1, Collecting and Handling of Natural Gas Samples for Custody Transfer, provides practical guidance for gas sampling in custody transfer applications. It is intended as a collection of lessons learned and best practices, and as such, it is a living document.

In support of this, API, the Gas Technology Institute (GTI), the United States Minerals Management Service (MMS), and the Pipeline Research Council International (PRCI) co-sponsored an extensive natural gas sampling research program at the Metering Research Facility (MRF), located at Southwest Research Institute (SwRI®). The body of this research was conducted between 1999 and 2005 and supported the most recent revision of API 14.1, published in 2006. Research into natural gas sampling has continued after the closing of the API 14.1 research project, and the standard will continue to be updated as the body of knowledge progresses.