Hydrogen flames can be nearly invisible in daylight, especially at low flowrates. The concentration of hydrogen does not have much effect on the color of the flame. Many hydrogen incidents or fires will have a bright orange hue, or even yellow flames. The color is primarily caused by contaminants that is either naturally in the air in certain environments, swept into the air during the release…

The answer is dependent upon the nature of the system and a hazard assessment which evaluates a balance of risk. 

Keeping the hydrogen in the vessel is better so the hydrogen release does not compound the original hazard. Large flowrates from vessels can create significant risk of vapor cloud explosion, jet explosion, or radiation exposure. Vent systems can also fail from poor…

Outside storage is generally considered safer and is required for large amounts of gas. Stationary storage should be located outside at a safe distance from structures and ventilation intakes, and protected from vehicle impact. 

Hydrogen storage separation distance requirements are typically based on the quantity and pressure of the hydrogen or the piping diameter, depending on the…

Sprinkler systems and other fire suppression means are prescribed per building and fire codes to limit fire spread to other materials. In the case of a hydrogen leak and fire, it is best practice to isolate the hydrogen source, and let any residual hydrogen gas burn out. Even if the initial fire is extinguished, additional leaking hydrogen may accumulate and ignite with the potential for an…

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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Static is a frequent source of ignition attributed to various hydrogen releases. Low levels of static
electricity are sufficient to ignite hydrogen – air mixtures. Static charges can be created by the
atmospheric disturbances and storms, high velocity particles entrained by the gas impacting stationary
objects, and human activity. Grounding of equipment and operators is important to…