I'm looking for anyone that has experience or an opinion on this storage system. 

I haven't seen it in person, but we have a Facility that wants to put this enclosure on their Helipad to fill a vessel incorporated in the helicopter to provide O2 to patients. The equipment inside the helicopter aside, I'm having a hard time finding relevant code sections for the storage and use in this instance. The system pictured is exactly the unit they are currently using at the airport. They are wanting to duplicate this here. The airport has not provided any info on compliance. 

I'm assuming concrete is required in the area where they are using the oxygen container. But I can't find a code directly related to this process. 

Here is where I have landed: 

99-2012 

Transfilling - I'm assuming this is a good description of the process. 

9.3.7.2 Outdoor storage/installations for medical gases and

cryogenic fluids shall be provided with ventilation per NFPA 55,

Compressed Gases and Cryogenic Fluids Code.

55-2016

8.13.2 Outdoor Storage.

8.13.2.1 General. Cryogenic fluids in stationary or portable

containers stored outdoors shall be in accordance with 8.13.2.

8.13.2.2 Access. Stationary containers shall be located to

provide access by mobile supply equipment and authorized

personnel.

8.13.2.2.1 Where exit access is provided to serve areas in which

equipment is installed, the minimum width shall be not less

than 28 in. (710 mm).

8.13.2.3 Physical Protection. Cryogenic fluid containers, cylinders,

tanks, and systems that could be exposed to physical

damage shall be protected.

8.13.2.3.1 Guard posts or other means shall be provided to

protect cryogenic fluid containers, cylinders, tanks, and systems

indoors and outdoors from vehicular damage. (See Section 4.11.)