It doesn't really matter here, but the lower explosivity limit (LEL) for hydrogen is 4% and the upper explosivity limit (UEL) is 75%. Basically, if you have an atmosphere which is 4% to 75% hydrogen by volume, it's explosive. If hydrogen is below or above that range, the atmosphere isn't explosive. Those are for hydrogen in air, not oxygen, by the way, and also at standard temperature and pressure, for the detail-oriented amongst us. For comparison's sake, gasoline has an LEL = 1 and UEL = 7.

On to the real issue, I agree with Mokele, although I'm not sure dropping a tank 100,000 times is enough of a test. I'd also like to know how it and all the downstream components handle long-term exposure to hydrogen. Hydrogen is bad stuff because it is highly reactive and can cause all kinds of chemical and structural mayhem. That's bad news for composites.

Don't trust manufacturers - a lot of underground piping installed at gas stations during the 80s-90s was damaged by contact with gasoline. The internal liner was resistant to gasoline, but the outer layer, which provided the piping's strength, swelled and came apart if exposed to gasoline. Unfortunately, the stuff was used in previously contaminated sites and new spills aren't uncommon. I'd like to think hydrogen tank design & construction would get more forethought, but experience says it won't. Especially when companies contract out the manufacture to the lowest bidder.