Flame arrestors can be installed on hydrogen gas vents. The purpose of a flame arrestor is to prevent the migration of flame backwards and upstream into the vent stack or system itself. Generally, flame arrestors are not needed since: 1) the vent stack should be designed to withstand fire or explosion within the stack, and 2) the process generally does not contain a flammable mixture within it…

Hydrogen vent stack fires can create NOx. While not typical, certain municipalities will require air permits to address the emissions from hydrogen flare systems, and even from intermittent ignition of vent stacks. This is highly dependent on the location and interpretation of regulations. A hydrogen flare system is much more likely to require an air permit than a standard vent system.

Heat tracing can be used as a safeguard against freezing. However, it must be understood that: 

• The heat trace system uses a utility supply so may not always be operational.
• The electrical equipment must be properly classified for the area, which can be challenging for the Div 1 classification for vent stack outlets.
• The heat tracing might be damaged by vent…

Yes, numerous incidents have occurred where frozen air (which contains oxygen) has built up within a hydrogen process or vent system. These incidents with vent systems incorporate more than just a vent stack, but include a vent system consisting of additional atmospheric equipment (such as a tank) where the equipment stays cold and allows air into the system in contact with a cold hydrogen…

Vent stacks must be designed for a fire at the outlet. The mesh is designed to ensure no blockage of the vent stack by animals/insects. 

Additionally, the mesh must be designed for pressure drop to ensure code-compliant back pressure on the relief devices.

Rupture discs open very rapidly. Historically, rupture discs opening at high pressure (1000 psig and above) have caused the most damage due to deflagration/detonation. Timing a rupture disc would not be possible. Additionally, how would you have a pilot light on a moving tube trailer? Even with a pilot light at the end of the stack may blow out due to the initial high velocity.

See…

In laboratories, 316 stainless steel tubing is frequently the first choice for small flow and pressures less than 2800 psi (19 MPa). See Best Practices: Material Compatibility for hydrogen compatibility with various materials. Always work within manufacturer’s pressure ratings adjusted for temperature. Read and follow…

There are several resources that can help review designs, such as the Hydrogen Safety Panel and other outside consultants that are members of the Center for Hydrogen Safety.

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

Electrolyzers should be installed per manufacturer recommendations and meet the criteria of their
listing, such as ISO 22734, Hydrogen generators using water electrolysis - Industrial, commercial, and
residential applications. There are several methods such as partitions, enclosures, ventilation, and
purging that can be used to address non-classified electrical equipment.