"This document addresses the safety issues that are specific to the storage of hydrogen in systems located underground.
Although it is preferable that hydrogen storage and related equipment is located above ground in a well ventilated area, this form of installation may be needed when it is beneficial to keep above ground areas free of equipment, such as may be the case for hydrogen vehicle refuelling stations.
This document covers the requirements specific to the installation of a hydrogen storage system in an underground space with top or side access, hereafter called a vault, including liquid hydrogen storage and ancillary systems and compressed hydrogen storage composed of a single container, or multiple cylinders or tubes.
This document does not address the generic design, materials and construction aspects of hydrogen pressure vessels.
The document is intended for use by all personnel involved in the design, installation and operation of hydrogen storage systems that may need to be located underground."