Filling and Purging Requirements for Advanced Media (22)

Filling and Purging Requirements for Advanced Media (22)

Criticality: Medium
Progress: Not Addressed
Score: 24
DOT Relevance: 173.302

Description of Key Area

Emerging hydrogen storage technologies (e.g., hydrides, cryogas, physisorption, and reactives) are being developed to address the low storage densityboth gravimetric and volumetricof gaseous hydrogen. Certain of these may require special handling when filling or purging. For example, heat transfer mechanisms are generally needed to remove heat generated during hydrogen charging for metal hydride containers. When purging (emptying) packagings containing hydrogen in advanced media, there could be a potential for a release of media or an inability to remove sufficient hydrogen (to remove any potential hazard) without removing the media.

Discussion of Criticality

It is anticipated that as these storage technologies develop, their proponents will determine any unique conditions or procedures for container filling and purging. It is also anticipated that as early products are brought to market, initial regulatory coverage will be via special permits which will likely require filling or purging to be performed by the manufacturer or their designated agents, providing a level of control over the filling or purging processes through manufacturers developed practices.

Discussion of Progress

As most storage technologies based on advanced media are not widely deployed (if at all), progress was assessed as Not Addressed.


As development and deployment activities increase, initially the special permit process could be used to incorporate any special handling requirements during filling. With sufficiently wider deployment, requirements could be considered for incorporation into regulatory structures.

Unless a particular filling or purging procedure could result in the development of a potentially hazardous situation, specific guidance may not be necessary.