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…

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…

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…

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…

In general, indoor storage should be limited and the use of hydrogen indoors should be the least necessary. Look to store flammable gases outdoors in dedicated protected area when practicable. Check to see what adopted building and fire codes in your jurisdiction say. NFPA 2, Hydrogen Technology Code, Sections 6.4.1 and 16.3 prescribe requirements to limit hydrogen storage and use in…

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…

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.