A closed container designed to hold gases or liquids at a pressure greater than ambient pressure. Pressure vessels are used in a wide variety of applications including compressed air receivers, distillation columns, autoclaves, and as storage vessels for liquefied gases such as propane, butane, chlorine, ammonia, and LPG. Pressure vessels are broadly divided into simple vessels and those that have more complex features. Simple vessels have a cylindrical body with dished ends and no supports or sections; they are classified based on the product of pressure and volume: Class I: 3,000 to 10,000 bar litres; Class II: 200 to 3,000 bar litres; Class III 50 to 200 bar litres. More complex pressure and higher-pressure vessels follow accepted international design codes such as the Pressure Equipment Directive legislation and EN13444 design code in the European Union, the ASME Boiler and Pressure Code Section VIII in the US, and BS PD5500 in the UK.