A7. Alarm levels

Alarms associated with hydrogen detection should be set as low a level as possible (≤ 10% LEL) without causing false alarms and should provide time to respond in a appropriate manner. Where the detection/shutdown system is a key part of the risk management system it should conform to an appropriate standard, e.g. EN 50073:1999 [7].
Hydrogen system operators should have a portable hydrogen detector available for their use.

Once an alarm is triggered shutdown of the system should occur as quickly as possible to minimise the hydrogen inventory and hence the potential consequences of an ignition.

Ideally alarms should be audible and visible. Automatic corrective actions are actions that can be automatically triggered including forced ventilation, isolation of electrical components, isolation of hydrogen storage and auto-shutdown.