Please note that the API Monogram Program effective date for the this document's next edition is November 2019. Until then, this edition will still be considered active and not historical. This International Standard provides the requirements for subsurface barrier valves and related equipment as they are defined herein for use in the petroleum and natural gas industries. Included are the requirements for design, design validation, manufacturing, functional evaluation, repair, redress, handling and storage. Subsurface barrier valves provide a means of isolating the formation or creating a barrier in the tubular to facilitate the performance of pre- and/or post-production/injection operational activities in the well.The subsurface barrier valve is not designed as an emergency or fail-safe flow controlling safety device.This International Standard does not cover installation and maintenance, control systems such as computer systems, and control conduits not integral to the barrier valve. Also not included are products covered under ISO 17078, ISO 16070, ISO 14310, ISO 10432, ISO 10423 and the following products: downhole chokes, wellhead plugs, sliding sleeves, casing-mounted flow-control valves, injection valves, well-condition-activated valves or drill-stem test tools. This International Standard does not cover the connections to the well conduit.This document is the Modified National Adoption of ISO 28781:2010, Petroleum and natural gas industries - Drilling and production equipment - Subsurface barrier valves and related equipment, with the addition of the API Monogram Program annex.