Exactly, the lower limit, when hydrogen has escaped into the air, not when air has leaked into the contained hydrogen. The article makes clear that above 75% H2, ignition is impossible (but only if you read it).
"Traveling along grain boundaries" can only leak trace amounts. With, as I said, positive airflow, trace leaks can be constantly diluted below the concentration where ignition is possible.
Comments
Exactly, the lower limit, when hydrogen has escaped into the air, not when air has leaked into the contained hydrogen. The article makes clear that above 75% H2, ignition is impossible (but only if you read it).
"Traveling along grain boundaries" can only leak trace amounts. With, as I said, positive airflow, trace leaks can be constantly diluted below the concentration where ignition is possible.