Is there a maximum hydrogen flow rate that can be vented to the atmosphere? For big electrolyzer systems, it could be necessary to route these streams to a flare system.

There is no maximum flow-rate that can be vented to the atmosphere, but the hazard analysis should consider the potential risk of dispersion, radiation, and overpressure as part of the vent system design. Flare systems are often used at large hydrogen production facilities as one means to prevent a large unignited cloud from forming but will depend on the specific application.