In order to easily use the valves, remove the cylinders and access the connections or regulating devices it's recommended that the opening into your cylinder locker or cylinder housing is sufficiently large.
If cylinder lockers are in high risk areas and they leak near sources of ignition, this could potentially cause a fire or explosion. To help prevent this happening the opening into a cylinder locker must not be situated in an accommodation space, engine space, fuel tank space or battery space. Boats manufactured before 3 January 2000 that were designed and constructed with a cylinder locker within the hull of the vessel, but outside engine, fuel tank, or battery spaces, are exempt from this part of the Standard. [7.6]