Gas Cylinders

Storage of Gas Cylinders: We currently have three gas cylinders - Hydrogen - DG 2.1 (size E), Oxygen - DG 2.2 & 5.1 (size D) and Carbon Dioxide - DG 2.2 (size D) which are secured with chains on trolleys. They have always been stored in the science prep area together, but I have now separated them so that the Hydrogen Gas cylinder is at one end of the prep area and the the Oxygen and Carbon Dioxide are together at the other end of the prep area. The MSDS says (among various other conditions) that they need to be stored in a well ventilated area, away from sources of ignition. The Hydrogen cylinder is near a bench with power points and a gas tap as this is the most practical location available. Can you please advise me if this is an unsafe practice? Also, there has been a practice of leaving the tap which controls the opening and closing of the valve in the open position and just shifting the lever to the off position to turn off or on. Is this safe, or should both sources be turned off?