Because hydrogen leaks frequently ignite, and because about half the time the ignition source is not identified, when evaluating hazards with hydrogen leaks, many people just assume the leak will be ignited. Note that consideration needs to be made for what may happen with immediate ignition (jet fire) and what may happen with delayed ignition (explosion). 

It is still important to…

See H2Tools, Best Practices: Purging, for a description of different purging approaches for hydrogen systems.

If the concentration of hydrogen is less than the Lower Flammability Limit (LFL) of 4% in an inert gas, it is unlikely that a leak of this gas mix will form a flammable mixture as it dilutes into air. For example, industry uses ‘forming gas’, a mixture of 4 to 5% H2 in nitrogen, as an oxide reducing agent in materials processing furnaces and soldering operations. This mixture can also be used…

The key concern with any hydrogen release is the risk of creating a flammable mixture. There should be no environmental issues if you properly vent hydrogen to a safe area where it is diluted in air below the flammability limit before contacting an ignition source. Very small quantities of hydrogen are frequently releasing into a fume hood. Releases have to be small enough so that the vent air…

Using tools inside a fume hood that may have a flammable gas mixture should be prohibited. A properly operating hood of the right capacity should keep the mixture of hydrogen in air inside the hood below the Lower Flammability Limit (LFL) of hydrogen further reducing any risk. 

If the use of tools is necessary, the source of hydrogen should be isolated before the work begins even if…

Frequency and severity off consequences are situational and subject to the safety review team’s best judgement. One measure of severity is an estimate of the energy released if ignited. Assuming the worst-case mix to be stoichiometric, the energy content of a 500 mL of hydrogen in air is about 0.2 Wh (700 Joules), comparable to the energy release of a wooden, blue-tipped matchstick (~1kJ or 1…

After moving people to a safe location, if it safe to do so, isolate the source of hydrogen feeding the fire. Burns and explosions are hazards when exposed to a hydrogen fire. For more best laboratory preventative safety practices as well as first responder response to a hydrogen incident See both CHS training resources: 

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Flare-less compression style fittings are commonly used. Choose tubing materials and tube wall thicknesses suitable for hydrogen and pressures you are using. Make sure all tubing joints are properly made, mechanically supported to minimize stress and vibration, are in a ventilated space, and are easily accessible for inspection and leak testing. 

Store flammable gas cylinders such as hydrogen, separated from oxidizing (e.g. oxygen), toxic, pyrophoric, corrosive, and reactive Class 2, 3, or 4 gases. Non-reactive gases, such as helium, may be co-located. See codes and standards such as NFPA 2 [7.2.1.1 Incompatible Materials] for further guidance.

Applicable EU Directives frequently include the following:

·        Low Voltage - 2014/35/EU

·        Machinery - 2006/42/EC

·        Electromagnetic Compatibility - 2014/30/EU, EMC

·        Pressure Equipment - 2014/67/EU

·        Restriction of Hazardous…