API Chapter 14.3 is a living document, constantly reviewed and considered for revision as new information and/or research data become available relative to the design and operation of orifice metering systems. In spite of this scrutiny within theAPI, AGA and ISO, the latest recommendations and revisions are not well known in many areas of our industry – and they were changed again during 2011.Many companies are still designing to AGA 3 1985standards or internal standards that do not meet current API recommendations.