Why is it important to turn off ignition at the scene of a hydrogen leak?

Turning off the ignition at the scene of a hydrogen leak is crucial primarily to prevent a fire or explosion. Hydrogen is a highly flammable gas, and when it mixes with air, it can create a combustible mixture. If any ignition source, such as a running engine or electrical spark from the ignition system, comes into contact with this mixture, it could lead to a fire or even an explosion. Therefore, switching off the ignition eliminates one of the possible ignition sources, greatly reducing the risk of a catastrophic event at a scene where hydrogen is leaking. This safety precaution is a fundamental aspect of responding to incidents involving hydrogen and is essential for ensuring the safety of both emergency responders and any bystanders present.