Oxygen leaking in is not an explosion risk. As noted, it takes 25% O / 75% H before it can ignite. Above 75% H it cannot.
With positive airflow around possible leaks, sufficient H2 to sustain a flame can be prevented. In a collision, gas released goes up and out of trouble.
With positive airflow around possible leaks, sufficient H2 to sustain a flame can be prevented. In a collision, gas released goes up and out of trouble.