ISO 28781:2010 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. ISO 28781:2010 does not cover installation and maintenance, control systems such as computer systems, and control conduits not integral to the barrier valve. Also not included in ISO 28781:2010 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. ISO 28781:2010 does not cover the connections to the well conduit.