There is limited published research on the effect of water sprays on hydrogen deflagrations and deflagration-to-detonation transition, and more extensive data on water spray effects on hydrocarbon gas explosions. The results show the benefits, where there are benefits, to be highly scenario dependent. For example, Carlson et al. (Atomics International report, 1973) described hydrogen…

The lesson learned (LL) article referenced in the question cites an incident that occurred in December 1969. While there may have been other accidents, the HSP does not have any other LL articles on alkaline water electrolysis explosions. In the LL article that was updated in 2017, the technology described employs a potassium hydroxide (KOH) electrolyte solution. The KOH electrolyte is held by…

Previous versions of NFPA 55 listed overhead power lines within the separation distance tables with no voltage distinction. The separation distances were 15 ft for GH2 and 25 ft for LH2 for all overhead electrical lines. The current edition of NFPA 2 includes these in overhead utilities; the distance for GH2 and LH2 will vary with pressure and diameter of the hydrogen piping. In practice, high…

The Global Asset Protection Services (GAPS) standard was written 20 years ago for property loss prevention at crowded chemical plants and is intended for existing and new oil and chemical facilities to limit explosion over-pressure and fire exposure damage; thus, the purpose is different than NFPA 2. NFPA distances were based on studies from the 1960s as well as qualitative factors that were…

There is technically no upper limit for GH2 storage listed within the separation distance tables within Chapter 7 of NFPA 2. For LH2, there is a 75000-gallon upper limit for the LH2 storage separation distance tables within Chapter 8 for LH2. 
It’s important to note that many facilities have site specific issues such as large quantities, confinement, and congestion, so it may be…

These distances are based primarily on hydrogen piping releases and resultant vapor clouds and jet flames based on pipe diameter and pressure. It’s important to note that many facilities have issues such as confinement and congestion, so it may be applicable to apply contemporary engineering models to assess risk.

NFPA 2 has provisions for the use of LH2, and there are many existing fueling stations that store and use liquid hydrogen. One challenge for the use of LH2 in stations with small footprints is the code required separation distances from exposures. NPFA 2 has updated the separation distances with a risk informed approach in the 2023 edition.

Another possibility for public fuel…

Regarding cylinders, it is not necessary to capture the fuse-backed devices which are on the cylinder itself. However, all other relief devices and vent valves must exhaust from a vent system designed in accordance with CGA G-5.5. Also, note that NFPA 2-7.1.17 requires compliance with CGA G-5.5 regardless of storage quantity when the vent system is servicing pressure relief devices. Cylinders…

The vent system for the excess hydrogen should be vented in accordance with NFPA 2 and CGA G-5.4 and G-5.5. The oxygen also must be vented safely and should be in accordance with NFPA and CGA G-4.4. 

Please be extremely cautious with compressing hydrogen. NEC/NFPA 70 and its Articles 500/505 address electrical equipment in flammable atmospheres. Please also consider the…

The British Standards Institute (BSI) has published BS ISO 22734:2019, a British nationalized version of the packaged water electrolyzer safety certification standard. This standard can be used by a Notified Body (BSI is one of many operating in the UK and in Europe) to certify electrolyzer safety to established norms for this equipment. This standard addresses safety of containerized hydrogen…