The purity required will be a function of the end use application. There are a variety of grades of hydrogen that can be purchased. The H2 purity will also vary based on source (GH2 or LH2) and production method. CGA G-5.3, Commodity Specification for Hydrogen, lists several typical purities of both liquid and gaseous hydrogen. Standard GH2 available from most suppliers is 99.95% hydrogen.…

The most common means to warm liquid or cold gaseous hydrogen is the use of ambient air vaporizers using ambient atmospheric. Other means can be through the use of electric heat or process waste heat.  

A design condition for vent stacks is to always assume that the hydrogen will ignite. The stack musts be designed such that it can withstand those conditions as well as minimize radiation to surrounding personnel and exposures. Although hydrogen fires have comparatively low radiation compared to hydrocarbon fuels, the radiation from large releases from vent stacks can be quite high. Documents…

Typically, the inner vessel material used is 304 SS and the outer vessel is a combination of 304 SS and carbon steel depending on location. 316 SS or 316L material can be used, but due to higher cost and lower strength, are typically only used for higher purity systems. Nearly all tanks manufactured today use various forms of vacuum jacketed multilayer insulation for best performance. Older…

Off gassing of hydrogen from battery sources depends on battery chemistry, usage/duty cycle, age, and other considerations. The specific battery manufacturer should provide recommendations for fire prevention and mitigation in battery charging rooms as the battery itself impacts how an event would be mitigated. Adequate ventilation such that combustible mixtures cannot develop is a general…

Catalytic recombiners are effective at preventing flammable hydrogen mixtures and also sometimes useful to monitor hydrogen concentrations through heat evolution when an oxidizer is present. Careful considerations must be made when integrating these elements into a design, so that they do not become a source ignition (and/or flame arrestors prevent propagation of a flame front) and the…

Even if a small experiment is being run inside a fume hood, the best practice is to use a dedicated vent line for hydrogen which vents hydrogen to a safe location outside.  This is especially recommended for planned venting.   This practice avoids situations where flammable mixtures could develop. Each system is unique and should be evaluated and approved for  use independently…

A nitrogen purge is generally not needed for a vent system designed in accordance with CGA G-5.5.  However, there are times where this might be considered or required due to the specific design of a system.  Where determined by a risk review to be needed, A continuous purge into a vent system reduces the probability air or oxygen in the piping. Intermittent purging should be…

The UN ECE R134 regulation is a good requirement to follow as it copies the language in the UN GTR #13 regulation. The updated version of this UN document (UN GTR #13 Phase 2) is currently in approval review at the GRSP in Geneva and should be approved by the end of 2023. Nevertheless, since the US Department of Transportation’s National Highway Traffic Safety Administration is a contracting…

Because hydrogen is labeled as a hazardous substance, sometimes people are concerned about the environmental impact of releasing liquid hydrogen. There are currently no regulations that require reporting of hydrogen releases for environmental reasons.

However, there are safety implications. For example, the US DOT requires reporting of hazardous materials releases under certain…