Because the bottle was located outside at the time of the event, and the hydrogen did not find a source of ignition while venting through the relief valve, nothing serious happened. The failed regulator was replaced and operations continued. However, if this had happened indoors or an otherwise enclosed space, the outcome could have been much worse.
The installed pressure relief valve and the small size of the orifice in the regulator (although allowing high-pressure gas to the low-pressure side of the regulator the mass flow rate is rather low) should be adequate protection of the rest of the system.
The key aspects of what can be learned from this near-miss can be emphasized as follows:
A regulator is not a safety device. Without additional protection, downstream components can be exposed to pressures exceeding the set pressure up to the full bottle pressure. If items downstream of the regulator are not rated for full bottle pressure, it is recommended that protection be added to the system.
Pressure relief device discharges need to be routed to a safe location. In the event of a pressure relieving event, it is important for the flow to be directed away from personnel, preferably such that the shut-off valve can be accessed safely.
Adequate ventilation is an important consideration in the layout of a compressed gas system. Inert gases (as potential asphyxiants), toxic and flammable gases can pose a significant hazard if not properly ventilated.