<P> A pressure vessel used for The Boeing Company's CST - 100 spacecraft . </P> <Ul> <Li> Natural gas storage </Li> <Li> Gas holder </Li> </Ul> <Li> Natural gas storage </Li> <P> Depending on the application and local circumstances, alternatives to pressure vessels exist . Examples can be seen in domestic water collection systems, where the following may be used: </P>

When does a vessel become a pressure vessel