Even then. Hydrogen quickly moves upwards. If it is a ground storage, any burning should happen above the storage and not enter it (at least in theory). And you

Even then. Hydrogen quickly moves upwards. If it is a ground storage, any burning should happen above the storage and not enter it (at least in theory). And you can measure changes in pressure quite easily. I mean, it is not like hydrogen storage has not been done for more than 100 years.