The British Standards Institute. Standards published by this organisation are denoted BS and are generally followed by a number and date e.g. @BS341. Part 1 1991 - Valve fitting for compressed cylinders. Over a hundred standards are relevant to cutting and welding and relate to design, inspection, testing and maintenance of cylinders and equipment ... Found on http://www.bocindustrial.co.uk/bocindustrial/technical/glossary/b.html