Plumbing the system to the outside is the better alternative from a safety concern. The best is a hydrogen generator, small amounts of H2 generated as needed. Safety issues are: A fire in a lab (what happens to a H2 cylinder), Moving the cylinder from the loading dock to the lab (usually involves several people handling the cylinder along with proper mounting and storage, a leaking cylinder, controlling access to the cylinder and connecting the cylinder all are safety concerns. There are some draw backs also but they have more to do with usage rather than safety like what happens when the cylinder is empty and how fast they can it be changed out but that can be addressed by correct design. An unseen leak with a piping system  will always be a concern.. Over all, a location away from people would in most causes be best with properly train personnel who handle cylinders on a regular basis. Costs are always a concern. A H2 generator may be cheaper that piping. These have been my experiences with H2 cylinders.